zug55 Loc: Naivasha, Kenya, and Austin, Texas

The two questions are connected. The D500 has 20.9 Megapixels. I don't think that there are any APS-C cameras with more than 24 MP, certainly not in the DSLR world. So if OP want more mexapixels that means looking to full frame cameras.

CHG_CANON Loc: the Windy City

Although not relevant to this question about Nikon DSLRs, the EOS 90D has pushed the cropped-sensor options to 32.5MP.

cahale Loc: San Angelo, TX

Why are you concerned with mirrorless? The mirror, or lack of one has nothing to do with sensor size (actual or pixel). Pick the pixel count you want and buy a camera that gives you that.

ecurb Loc: Metro Chicago Area

I think the APS-C sensor has seen its day and soon will be a niche sensor at best, along with M43 and smaller chips. Now that full frame and larger sensors are reliably manufactured in a shrinking camera market the need for APS-C and smaller sensors is gone.

DavidPine Loc: Fredericksburg, TX

Go with the current D850 FX and you won't be unhappy. It is a proven winner. Things will go mirrorless and you might consider the Z7ii.

Thomas902 Loc: Washington DC

Rick Benson you have only one viable choice...
The Nikon D7200 which not only has a higher pixel count but also far better dynamic range...
Carefully study DxOMark's analysis of the D500 verse the D7200... 14.6 verses 14.0
It's even higher than the D750's dynamic range of 14.5. Besides the D7200 actually has better low light performance than the D500 but only but tad...

https://www.dxomark.com/Cameras/Compare/Side-by-side/Nikon-D500-versus-Nikon-D7200-versus-Nikon-D750___1061_1020_975

That said, if you are into printing large, why?
Do you actually have clients which request same?
Or are you simply shooting on "Spec" hoping you'll find buyers... (been there, not a wise scenario btw)
I only shoot by a mutually agreed upon contract now... Experience is a brutal teacher...

As for APS-C? I've repeatedly heard (hearsay, not corroborated) that it is an issue of pixel pitch that limits...
A.K.A. the D850 has the same pixel pitch as D7200... In fact you could shoot the D850 in DX mode with likely similar effect...

Hope this helps...
And please consider selling your DX glass here on UHH...
I might be interested!

zug55 Loc: Naivasha, Kenya, and Austin, Texas

"The mirror, or lack of one has nothing to do with sensor size." Very true. But sometimes being a little proactive is useful. If OP wants a higher pixel count the only way is to go full-frame. Once you go full-frame, you might as well go mirrorless rather than investing in an obsolete full-frame DSLR system.

zug55 Loc: Naivasha, Kenya, and Austin, Texas

The D850 is a great camera--I nearly bought one three years ago when I came to my senses and bought a Sony A7 III instead. Things will not go mirrorless--things went mirrorless. Why invest good money in a DSLR system that has no future?

Wingpilot Loc: Wasilla. Ak

It would require you to switch brands, but the Canon 90D has a 32.5mp sensor. The 90D is a crop sensor camera.

CO

The dynamic range advantage was only up to about ISO300. After that, the D500 had wider dynamic range all the way to maximum ISO.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

I worked for Nikon back before dirt was invented. I still have contacts with Nikon and have heard nothing. Nikon is fully committed to their Mirrorless line of camera's and lenses.
No one knows where the Nikon camera division is headed in the long run.
I still own the D500 and D850. I shoot primarily wildlife and use the Nikon 500mm f5.6 lens with the D500 giving me a field of view of 750mm with the D500. I have done 24X36 aluminum prints from this combo with fantastic results.
I have also moved into Mirrorless with Sony. I shoot with the 24 meg. Sony a9. Soon Sony will come out with the Sony a9III that will have the megs of the Sony a1 but will not have a mechanical shutter, rather it will only have a electronic shutter, that is fine with me.
So, to sum up, for the current time I see no new APS-C DSLR coming from Nikon. But who knows, they could come out with one at any time. If I were you I would buy no new APS lenses for the foreseeable future.
Good luck and keep on shooting until the end.

ELNikkor

Surprised that, being a large print printer, that you have not already gone to FX. It is high-time to get the most out of your large-print equipment and invest in Nikon's excellent FF Z cameras and lenses.

Drbobcameraguy Loc: Eaton Ohio

Everyone is on this mirrorless kick. Yes mirrorless is the future. Is it even CLOSE to being finalized as far as features and focus tracking ect ect ect? NO. Will mirrorless make enormous strides in the next 2 years? Bet your dlsr it WILL. Or better yet bet your current mirrorless camera. The mirrorless development cycle is at the beginning. So much more neat and useful things will be available in the next 2 to 5 years. My OPINION if you can just start saving money now if at all possible limp on with a state of the art dslr which can be had RELATIVELY CHEAP and in a couple years you can buy the camera that will blow anything available now out of the water. If you cannot possibly wait Sony is the leading edge today in my OPINION. Love that word. Lmao 😆. Why ? Because I can say anything about anything and if it's my OPINION I don't have to back it up with anything except the old saying about opinions. 😂

NormanTheGr8 Loc: Racine, Wisconsin

You could go with an adapter and a Sony a7R4 shooting in crop mode , I know not perfect but a viable option . Yes it's better to use native lenses instead of adapted

camerapapi Loc: Miami, Fl.

I predicted several years ago that eventually a majority of the cameras made would be mirrorless so I am in agreement with those that already mentioned that. If the DX and the FX sensor will continue to be manufactured in dSLR cameras I certainly do not know but the trend is toward mirrorless right now as it is very well dictated by the market.

The M43 system of Olympus and Panasonic does not seem to be dying soon. I have not heard of any plans by Olympus to abandon the present system in favor of a full frame camera. I know Panasonic introduced last year a mirrorless full frame and I do not know how successful it has been while Olympus CEOs have denied to be in the making of a full frame mirrorless. I am sure a majority of you know that Olympus has introduced the 150-400 f4.5 and the 8-25 f4 as part of their lens road map for their M43 cameras.

In regard to the OP, although I have never used a D500 I have only heard good things about it. The same I can say about the D850. I am sure that the D500 with its 20 Mp. is very capable of producing excellent enlargements and I say this because going to the D850 will require selling all the DX lenses and investing in the FX format. I have made a few big enlargements from my Olympus cameras sporting only 17 Mp. and from the distance those images are usually look at the resolution is more than adequate. In my book 20 Mp. are a lot of pixels. It is very possible that with 45 Mp. a new computer with a more powerful processor is needed and those files surely will take a lot of room in the SD card and the computer.

I remember been very happy with my enlargements coming from the D2H with only 4 Mp.