Megapixels should be the least of your concern. It's mostly a marketing ploy, but it has some importance when you're looking at printing large.
I think the XT will serve your purposes just fine, and unless you NEED to shoot video, or NEED a new camera body because yours is faulty, then I'd save your money or invest it in glass. Buying a new camera body will not help you learn the principles of photography any better, it also won't make your photos better.
Like I said before, focus on the fundamentals.
Learn ABOUT your camera, and then apply that knowledge and learn FROM your camera. You'll be glad you did. :thumbup: