Im waiting for 650D announcement until i decide on my first DSLR: if it is going to have a new sensor, ill probably get it, if not, i will most likely take used 550d (cheapest one with the same sensor) and a good lens.
I wouldn't bother waiting, no new camera will compensate you for the shots that you will miss in the meantime. If we were all expecting the 650D to be a quantum leap in performance, then you might have a reason to hold off buying, but generally Canon do not introduce their latest technology on the 'Rebel' bodies. Buy a body now that appeals to you, be that Canon, Nikon, Sony or whatever.
My second piece of advice, if you think that photography will be anything more than a passing interest, is to buy the next level up in the range (of whichever brand you decide upon). I made the mistake with my first DSLR (a 450D) and within a year wished that I'd gone for a 40D or D90 instead. It isn't a big difference in price compared to the improved ergonomics and performance that you get in return. O.K. if you're really skint I can see the reasoning for an 'entry-level' model, but I'd still be tempted to recommend a second hand, higher spec model from the previous generation in most cases (I wouldn't go too old though -30Ds and D80s are a bit on the dated side now).