Overall, good glass is going to be a better long-term investment, but body upgrades are a fact of life. Unfortunately, you have to do both at the same time. One possible path is to do a modest body upgrade now (T4i?, 7D?) and put the rest of your money into some good lenses (85mm f/1.8, 24-105mm f/4, etc). That'd improve your shots all around and would still give you better ISO performance, AF, FPS, etc. Then, when you make the jump to full frame, you'll have a few decent lenses to make it worth it.