Whether Leopard features are revealed now or in October might make the difference whether or not Microsoft can copy them in time for whatever, if anything, follows Vista -- sometime in the next decade.
I expect the next MBP speedbump to coincide with the release of Leopard and to include higher resolution displays and slightly faster processors. 800MHz DDR3 memory would be nice if Intel adds support for it to Santa Rosa (disabled at the last minute due to stability issues). I don't expect any other changes this year.
At the moment 1x 2BG is much more expensive than 2x 1GB because the former uses newer generation chips. Apple might in the future offer a 1x 2GB option for an additional $100 or $200 or so. I believe there are precedents for this.