re: video limits and "best" quality video
Yes, there's a limit of 30 minutes per take and 4GB file size, which ever is reached first. As Bob noted, the 30 minute limit is due to Canon not wanting to pay higher taxes in the EU and not wanting to produce different models for the EU and the US (like Panasonic does, for example). And the 4GB limit is due to Canon not implementing file chaining (again, like Panasonic does) on most of their DSLRs.
Having said that, keep in mind that, when recording is stopped due to either of the above limits being reached, you can just start recording again (so neither limit will prevent sensor overheating, which is another limit that can shutdown the camera, but you will not be able to immediately start recording again). (Note: Canon's 7D is particularly susceptible to overheating due to the combination of weather sealing and two DIGIC processors.)
As for "best quality video available" -- how much money do you have? There are professional cameras like the Arri Alexa or Red Epic. Or prosumer cameras like the Sony FS700 or Black Magic Production 4K camera. Or the folks at Magic Lantern have recently hacked the Canon 5DIII (and 50D) to output RAW video. Or there's Black Magic's Pocket Cinema Camera which also does RAW video. Or you can buy a Panasonic GH3.
Of course, as a general rule, the more sophisticated the camera, the more involved post production gets. (e.g. Red Code requires it's own workflow. And processing 4K video is extremely resource intensive. Even RAW video from a hacked 5DIII has some quirks.) So you'll need to increase your budget here, as well.
But, as I said previously, for what you plan to do, I think a T4i will be fine, as long as you light the scene properly and capture good quality audio (and don't mind dealing with Canon's take limits).