The MBP and MB will last the same time, both are good in terms of power. I am also wishing for a Blue-Ray (should be standard) burner in the MacBook and MacBook Pro.
No, they will not last the same time. Physically, probably. But a MBP will run new programs at acceptable speeds further into the future than the MB. Blowing it out of all proportion, a 3Ghz Mac Pro will be able to run more programs in say 5 years than a Mac Mini. Same goes with MB and MBP. MBP has higher specs, and so it will take longer before programs have higher minimum system specs than it does, than it would for the MB.
Think we'll have to wait a couple of years to have Blu-Ray burners in MBP's.