The driving force here is that the phone does need to be capable of being an independent computing unit, so that tends to force things onto the phone. A new GPU and CPU etc may be nice, but for most people won't be necessary, and I suspect your average clamshell simply won't have it. I think the general case will be dumb clamshell with nothing but peripherals, USB ports, and a battery. The alternative is significantly more expensive, yet brings the average user no benefit. (Possibly negative if its less reliable.)
A clamshell that does have everything in it will simply be a laptop, and laptops will continue to outclass phones in raw performance for a good long time. (The presence of additional, usable volume will continue to be an advantage for a good long time yet, and by volume I mean literally three-dimensional space.)
A clamshell that does have everything in it will simply be a laptop, and laptops will continue to outclass phones in raw performance for a good long time. (The presence of additional, usable volume will continue to be an advantage for a good long time yet, and by volume I mean literally three-dimensional space.)