You need to figure out what your budget is, and what lenses and accessories you will want for video. Lenses get expensive very quickly. Some other things that could add to your budget include support (tripod, pan/tilt head for the tripod, and/or stabilization rig), extra audio gear (the on camera microphones are not very good, nor are the on camera audio recorders), possibly some lighting.
My advice would be to get the newest model Rebel. That way you don't spend much on the body, and you get the latest iteration of video tech in the body. Most of the advantages of the 7D over the rebelbodies aren't relevant to video (for example, better AF system, autofocus micro adjust, better controls for stills and better optical viewfinder won't help you with video). Keep the focus on the overall kit, you don't want to blow most of your budget on the body and do the rest as an afterthought.
Look up magic lantern if you're not familiar with it. I don't think it works with all models, so that is something you will want to check.
For stills, I'm not a fan of buying the newest, shiniest body, but Canon's video support in DSLR (as opposed to stills, the traditional function of these cameras) is still very much in its infancy, so I'd be all for waiting and seeing what comes next.