I started with a D1x in 2001 and then upgraded as each new model came along; D2h, D2x, D2hs and then D700 for my first fx sensor model.
The menus and controls of those cameras became second nature to me.
When I got my D750, I had to relearn which menu is located where to maintain manual control. There's enough difference in menus and interface between the "pro" D800, 810 and the "not quite pro" D750 to warrant consideration.
That covered, I LOVE my D750 for its quality 1080p video and 24mp high-iso stills. 4K would be nice. If and when Nikon introduces one that shoots 4K and is as reasonably priced as the D750, I'll buy it, despite the menu interface issues I continue to adapt to.

I believe that the MacBook Pro Retina is all soldered in. Since my photos library continues to grow, no longer concerned with the cost of film, processing and printing, I keep my library on a 1TB USB3 drive for which I then maintain a faithful backup on a second identical drive using SuperDuper (or Carbon Copy Cloner). Because I also shoot 4K video with my iPhone 6s, that content goes directly into my Final Cut Pro X libraries for which I do the same cloning on 2TB USB3 drives.
I do the same for my 260GB iTunes library.
It's always a good idea to maintain at least 10% of your internal storage media free for internal OS maintenance performed by the under-the-hood UNIX which makes the Mac so reliable and stable.

El Capitan is the latest iteration of the 64-bit operating system front end for Unix. I've found no issues or problems moving from OS to OS. I do, however, perform a Time Machine backup before each upgrade, just in case something goes terribly wrong and I have to revert to the last backup. That happened with one beta version of Mavericks and Apple ProApps which was resolved within less than a week.
As for getting a new Mac, you'll probably have to deauthorize/uninstall the old one's Adobe applications so your PS6 is available to activate on the new one. When you get your new Mac, you can even restore it from your Time Machine backup and expect to have everything where you expect to find it, with the exception of reserializing the newly activated Adobe applications. If you buy from an Apple Store, you should even be able to get guidance/assistance on setting up the new Mac or for $99, they (we) will do the data migration from old to new for you. But it's a task that you should be able to do yourself, following the simple onscreen prompts when you start up the new Mac.
One more thing, Apple is introduced a new free Apple support service, available 24/7 via chat or phone support for all Apple products - getsupport.apple.com
Congratulations and happy holidays.

And I love my Epson 3880 for both quality and color accuracy.

You may also consider looking at Affinity Photo and MacPhun's various image editing tools, all available at reasonable prices.

I understand where you are coming from. However, I've been an integral part of this as a working, professional digital photographer since 2000, traveling through several different Nikon models including D1x, D2hs, D2x, D700, D750 and loads of different software packages until landing on Aperture, as well as being a Nikon Professional and Certified Apple Trainer. My ups and downs and lessons learned lead me to have no fears about the longevity of Aperture as a 64-bit application running in a 64-bit architectured Operating System.
Aperture can open your Photos Library and Photos can open your Aperture Library. And, thanks to Adobe, there's even an export tool to migrate your Aperture Library to Aperture if you prefer.
But, when we went to all 64-bit operations, based on UNIX, we left the door open to unlimited development.
On a related note, some of my customers are still using iWeb to develop and manage their websites despite the fact that Apple discontinued support for it four years ago. And despite the fact that we no longer deliver or support either iDVD or Final Cut Pro Studio 3 and all its associated applications including DVD Studio Pro, these tools are still in wide use and satisfying those who have them. All are 64-bit, not requiring any other resources besides the MacOS and, of course, a Mac. Those applications left behind were written in 32-bit mode. That's about it until we migrate to 128-bit software, but that's probably a looooong way off.
If you want to migrate to a different OS on a different platform, good for you. But Mac users with the current operating system have nothing to fear regarding "planned or unplanned obsolesence." I think it's safe to say we'er in it for the long haul.

Why not read new RAW files? The coding for those files is accepted in the MacOS and available to all applications that need it. If a new camera is released and new RAW formats are created, you can count on Apple to encourage the camera manufacturer to provide the needed code so it can be used by Photos, thereby enabling Aperture to do it's thing as well.
Generally, for companies such as Adobe and Microsoft, getting it right takes a little longer and drivers need to be compiled for each new piece of hardware and software. Apple, on the other hand, is and always has been, plug-and-play for both hardware and software.
Taylor Swift, "Haters gotta hate." But, please don't confuse me with the facts, I've already made up my mind.
Not a flame, just a hope that this doesn't spiral into a religious fight.

Here's the good news . . . , Aperture will continue to work as long as you continue to use it. It is a 64-bit application written to work as expected in the MacOS environment. Your library will continue to grow, additional plugins from OnOne and others will continue to work and you will be able to do all you've come to expect of Aperture.
Photos has many of the same editing capabilities as Aperture and was introduced to enable users with libraries larger than iPhoto could easily address to enjoy the benefits of fast image management and editing.
But, there's no need to change unless you believe that Aperture no longer works for you. My approach is, "If it ain't broke, don't fix it." The fact that Apple is no longer "supporting" Aperture shouldn't keep users from continue to enjoy its elegance and power. That's what I'm doing while I'm am also one of those who have been working with Mac users to learn to enjoy Photos as an Apple Creative. Photos is great. Aperture is great. They tell me Lightroom is great. My advice, use the tools that give you the interface, power and control you expect.

Sorry for the problem, Tony.
I can do a secondary click on an Aperture image and edit with Photoshop 6, save it, and when I close the document in Photoshop, it shows up as another image in Aperture. No renaming, exporting or file mapping change to .tif needed.
If you're shooting camera RAW, which I highly recommend, at least from Aperture to Photoshop and back, after closing the edited image in PS, then shows up again in Aperture, but now includes the Photoshop attributes including layers if I want to go back to Photoshop.

I'm using an iPhone 6s and Nikon D750 with no problems.
Apple must keep it's raw converters up-to-date at the OS level so that Photos can continue to support ALL photographers. And, of course, .jpg is .jpg.
Because the image file interpreters/converters are at the MacOS level, one should expect that all applications that use images, certainly including both Photos and Aperture, will work just as one would expect.
Please try to understand that the MacOS is essentially future proof and the only things that seem to have been left behind were those things that only worked in 32bit mode once Apple moved to all-64 bit operations.

Ditto, busmaster2. Been using Aperture in El Capitan with no problems since the first beta of 10.11. Now on 10.11.2 and NO PROBLEM with ANYTHING and Aperture works as always, seamlessly.

For Leitz' post:
Best laugh yet on UG!
Thank you.

I've printed hundreds of DVDs and the only brand I count on for a professional and lasting image is Tayio Yuden/JVC. I use a Primera Bravo and Discus software- both worth checking out.

Without digging too deeply, are you using a Mac and if so, what OS or a PC? I know how to fix this on a Mac

Well, OK. I had used that lens on a Nikon D1x, D2h, D2hs and D2x until I realized I need VR stabilization for my aging hands and arms. I was only responding to the logical, "is your device plugged in?" observation.