At some point, the folks at ML will have to start End Of Life, support for certain cameras. Too much new stuff folks want to use.
Not that I am an expert but here is the whittle down list ...
600D/T3i is the cheapest, HD 1080p camera, with both 3X zoom & swivel LCD. Still best value for low budget film.
Then there is the 7D which is fastest sports camera (8 fps). Trap focus / valometer for the wild life shooters.
Then there is the 70D, which is the only AF camera with 3X zoom & swivel LCD. It probably needs the least in terms of existing ML features, basically all that matters is RAW video and arguably HDR video.
6d - poor mans FF, definitely has legs.
5 MarkIII, the best FF raw camera.
But after this short list, I don't see any crucial cameras that will have legs for more adopters,
in terms of going forward at this point. JM2C.