It's fair to dream. I've no doubt the CPU core count will increase somewhat in the next iteration. I wouldn't be surprised to see more fixed function hardware in their next (theoretical) SoC.

I'm not sure if we'd ever really see that much gfx resource in a handheld, at least for now. I agree it would be very cool but vendors need to strike a very fine balance as far as power is concerned. Could go for the 'dock to unlock' approach though I genuinely appreciate that the steam deck's performance characteristics are 1:1 plugged in and on battery. Besides that, area is expensive, and the steam deck came in at an extremely attractive price in 2022 relative to other x86_64 handhelds on the market. I would hope price remains a focus to get Linux gaming and desktop experiences into more hands.

As for halo in particular, significant improvements have been made at a packaging level to minimise idle draw with the mcm design (and I think that is somewhat reflected in current OEM offerings) but it's still not quite where you'd want it to be in a handheld system. That's not to say it won't get there eventually.