Based on the photos you've posted I'm inclined to suggest you take a different route: 6D + 70-300L (or, if you really need f/2.8, the new Tamron 70-200). True, the 6D's autofocus isn't as sophisticated as the 5DIII's, but it should be just fine for the sorts of things you seem to photograph (in really low light it should be a bit better than the 5DIII, at least if you stay with the center point), and the images it takes in low light are in a completely different class from your Rebel (I owned the same one as a back-up for a while). As for the 70-300L, obviously it's not as good as a 2.8 if you need to freeze action, but it otherwise performs superbly in even very low light when attached to a 6D; and with the 6D's superb high ISO performance you'll be able to freeze action anyway, even if not as well. Assuming the reports that the 70D's ISO performance will be similar to the 60D's (and thus your Rebel's) are true (if so, that's very disappointing), I wouldn't bother waiting for that at all. Even if it's better, chances that it will be as good as the 6D seem remote - and, as you will have noticed, the price of the 6D seems to keep getting lower (if you wait for the right sort of sales).