i don't think a redesign of the 360 will do anything...maybe it's just me but i don't think the ps3 slim selling so well has anything to do with the redesign and everything to do with a price drop. that said, if MS can pull a price cut (and i'm pretty sure they can) it will do wonderful things for the 360.
as far as natal goes...atm i think the move looks better but let's wait until natal has at least one game announced before making any judgments on the success/fail of natal.