Being a computer science major graduate student, I feel that it is not an easy choice to make.
After eagerly waiting for this year's iteration, I was very optimistic that Apple would work out a way to squeeze in the i-core chips for 13" MBP. I have read the articles that explain their reason for not making the move, that being, the physical limitation of space on the small motherboard. However, Intel did design the Small Form Factor (SFF) Core 2 Duo chips for MBA to address a similar situation. They may do something similar with MBP 13".
Having said that, new things will keep on evolving and there will always be something better coming up. I think I would just go with it and buy the 13" as the pleasure of using the machine will easily outweigh the pain of waiting for the next iteration whose timeline is not certain. It may be this October, or December, or even April next year...
Also, I feel, the base model of 13" will only be "marginally" better than the base model of its next iteration. (e.g. new base model iMacs with i3... link:
http://www.macworld.com/reviews/product/586734/review/215inch_core_i3_imac306ghz.html. If we ignore the discrete graphics card and only consider the cpu performance, it is not a major performance bump.)