You should click "quote reply" not just "reply" so we know what message you are replying to. Reply is when you want to make a general comment to no one post in particular.

I have the 7DII and 6D. Both have their places, I love both cameras. The 5DIII has slightly more megapixels and a lot better AF than my 6D. But the 6D sensor is newer tech and does just a slight bit better in low light. It is also smaller and lighter than the 5DIII. Since they are starting to discount the 5DIII it is a good time to get one, unless you think you might have buyers remorse when the 5DIV (or whatever they call it) hits the market. Then too the rumors about a 6DII might make waiting a little a good idea. Rumors say they will both come out sometime next year, the 5 early in the year and the 6 late. Well, we will see.

I presently have the following lenses, all Canon. 24-105 1:4L, 24-70 1:2.8L, 70-200 1:2.8L and all have the IS feature except the 24-70, so I believe I'm in good shape with the glass I have. Are there any other lenses you would recommend? The reason I'm considering the Mkiii is because I've been told that for landscape photography, a full frame camera would be the way to go for the best results. And yes, I like to have a good back up camera and one with the higher fps for reasons stated. That's why I would want to keep the 7D Mkii.

Yes, I've heard that as a reason as well (for the FF) as lower noise at higher ISOs (in your case for indoor sports). For landscapes ISOs of 100 to 200 are just fine. Though I am wondering what you are using for a lens for your CF landscapes now. You may want to go a lot wider than your present set of Zooms. I'm not sure what Canon has available for CF wide angle prime lenses or zoom lenses, but look in the 10-20mm, 11-24mm range.

I have a vintage 19mm lens that on my CF Pentax DSLRs is not all that wide (equivalent to a 29mm FF or film lens, or 24mm equivalent to 36mm). Yet it is very wide for my old film cameras. No Pentax FF DSLR yet (perhaps coming later this year).

Are you meaning "35mm camera" to mean a Full Frame DSLR or a film SLR? Yes, I know the technique you are describing. But I am confused by your reply to my comments and question to the OP. I was asking him about the focal lengths he chooses for landscape shots seeing as none of his lenses would be particularly wide on a Cropped Factor DX body at 24mm. And only wide even on a Full Frame FX body at 24mm. I was not actually advising him to go FF or stay CF as I noted with how I worded my response. I was suggesting (implying) he opt for a wider lens and learn it before getting another camera.