That may be of embellishment, as they won't be "so much better"...if anything, anticipate a 10-15% speed increase with I/B. "It's a Tick, not a Tock" (quote directly from Intel)...Sandy Bridge was a major enhancement to the Core2Duo chip...and the 22nm process + the 3d transistor setup in I/B will be another achievement...however, MUCH that will come from that foundation is still a couple years down the road. I would suggest the "biggest" improvement to today's MBP line is the forthcoming integrated Intel 4000 Graphic Processor. As well, improvements in the 15/17" line of the existing "separate" GPUs (whether they be AMD or nVidia) will be the deciding factor in my purchasing decision. The OP...even with a late model (as suggested earlier in the thread) Core2Duo used model will notice an Extreme improvement in comparison with his/her 2007 MB.
The current line of Sandy Bridge MBPs are easily the most significant improvement performance wise (over their predecessor) than any processor I can remember. The 13" of this year is keeping pace or slightly out-pacing last year's 15 and 17" original core "i" structures!!! Their as fast as last year's entry level iMacs! Their incredible little machines...as are the Airs.
That said...we are a bit late in the life time of this batch of laptops...we're closer to a new one being introduced than this one's introduction last spring. However, I just wanted to make the point that buying now isn't going to yield a poor performing computer in comparison to what's coming down the pipe.
I do like the idea of holding out...if you can. Obviously, you're not reliant on your machine for school...yet. So, if you can get by surfing, checking email and FB til they DO drop the I/B lineup...my suggestion at that point would be to (if past indicators are the same) save 15-20% on a refurb unit of the current model! Best of both worlds...save a couple hundred bucks and get a new, refurb from Apple with this year's performance. Coupled with the education discount, your savings could be even more significant.
I understand impatience though...and the desire to have something faster and more sparkly

If you have the cash now, want the computer and don't feel like holding out...pull the trigger! It's a Awesome package available right now!
J