As for hardware, an update from the two Series consoles makes sense. Zen 3 is out, the new infinity fabric IP will be out by the end of this year, this years slight RDNA2 upgrade (supposedly 6nm and such) should be out. Further a shared very large (64mb ish) llc would make a lot of sense for a mobile console, cutting a good amount of wattage.
The biggest concern I can see versus the big consoles is the CPU. Eight cores and high clockspeed aren't exactly squishable. Even upgrading the arch is only going to do so much, all I can see happening in a 9-7 watt tdp is a quad core CPU with modest clock speeds. Still, as long as it's decently above last gen consoles I'm not sure many devs will mind, no more hyper optimization. Beyond that things like DSP hardware already in the Series can be pretty low power, modern EUFS flash storage is pretty comparable to NVME ssds. And
I'm guessing 9 watts because A. Microsoft has absolutely wonderful mobile cooling engineers (the Surface series might be dated in areas, but the cooling system is an engineering work of art) and AMD supposedly has a separate 9 watt mobile APU coming out this year anyway, one with an RDNA2 gpu rather than their current notebook lineup with "Vega+". As for hardware, an update from the two Series consoles makes sense. Zen 3 is out, the new infinity fabric IP will be out by the end of this year, this years slight RDNA2 upgrade (supposedly 6nm and such) should be out. Further a shared very large (64mb ish) llc would make a lot of sense for a mobile console, cutting a good amount of wattage.
Basically throw 10-12GB of lpddr5 mobile, say about 6400 for speed, in a mobile soc. Quad core zen 3 clocked at like 1.9ghz or so, maybe 16-18cu GPU (a double compute unit or two disabled for yields and tdp) clocked at around 1.2ghz. Throw in a 900-1080p OLED and you've got a mobile little speed demon for $400 or so. Battery life will be interesting to see, giant battery cells seem to have gotten relatively cheap thanks to phones, but of course that would add weight regardless.