I can see an eventual future when the cores, RAM and storage are all on one IC or something which would also be great for performance (I just bought a desktop processor that does some clever stacking of extra L3 cache on top of the cores). As others said though we're not quite there yet.

Ever since Steve Jobs (I think perhaps as a way of coping with illness making him thinner himself) Apple has done this thing of telling consumers that they want thinner, thinner, thinner at all costs (and other manufacturers following Apple because of course they do) but I've seen no real evidence of consumers actually wanting this. I for one (and I know I'm far from the only one) don't actually mind a bit more thickness if it means a bigger battery, using an M.2 slot (oh no a few mm difference) etc.