Given the right situation even a Canon Rebel can do that kind of shot - heck even an old 350D with the right lens in front of it and the right photographer behind can take some outstanding shots. The key is that higher end cameras have better specifications to get you those shots in more unreliable conditions.
The 7D can certainly do action photography without any problems, it even lets you customise your AF controls so that its more suited to the scene your shooting (A great one is to have the sensitivity of the AF getting a new lock on a new subject slower - this is great for following the motion of a subject, where if you waver off the subject or it rushes behind something for a second you don't want the camera to instantly lose focus and lock onto something else).
I can't speak for the Sony or the Nikon (I don't use them); however the points regarding high ISO are ones I would pay attention to - because with wildlife and action photography you'll be at ISO 400 - 800 very often and higher still if you need it. Noise you can correct for but blur can't be fixed in photoshop*
*sometimes you can fix it, but it requires a lot of work to get a good job done and most of the time you'd be looking at hours of work to correct a problem. Plus at that rate you might as well stop with the camera and just do straight digital art.