You Know Spin Doctor, at the rate Apple is going, and the problems between Intel and Nvidia, the Core i7 may not make it to the MBP for a LONNGGGG LONNNGGGG LONNNNNGGGGGG time.
I think in theory, the idea is great considering a 3rd or 4th Qtr possibility and then the MBP will be loaded with Snow Leopard and the 15" MBP will probably support 8 GB RAM then. Actually, I think the current unibody MBPs will receive firmware updates to accept 8 GB RAM. Apple offering 8 GB RAM in its iMacs today really gave the "Pro" user of the 15" MBPs a reason to complain if Apple doesn't enable the 8 GB RAM. Apparently it has nothing to do with hardware and everything to do with Apple's set limitations of what it wants to support.
But, all in all, at the end of the year, the MBP should be one bad ass machine with a Core i7 CPU and 8 GB RAM running a super efficient Snow Leopard!