And you know this because...?
Current mobile quads have TDP of 45W-55W while MBPs use 35W CPUs so there might be a drop in battery life. IF Clarksfield goes 32nm, we may see a 35W quad but if not, we have to till Sandy Bridge. Of course when 3 of 4 cores are idle, the battery life will be pretty good but under heavy load, the battery will drain a lot faster