AMD

If it's in 2-3 years, Zen 4c with RDNA3, hopefully with 3DVcache

If later, Zen 5c with 3DVache + RDNA 4.

It would have to be 3nm based as 5nm isn't enough of a jump from 7nm to give valve the performance jump they are looking for.

Zen5c cpu is the most likely CPU successor due to smaller die space than zen5 normal and how it won't need to boost to 5Ghz+ like in desktop/mobile SoC's.

RDNA 4 is the most likely GPU successor as RDNA3 is a dud and RDNA5 won't be ready in time for SD2(late 2025 IMO).

LPDDR6 is possible, speeds starting at 12800MT/s vs the SD OLEDs 6400MT/s.

Kraken Point coming after Hawk Point is supposed to bring Zen5 + RDNA3.5.

I was hoping the OLED model would come with a higher resolution screen but I guess Valve is also waiting for a more capable APU before they increase the resolution.

Given that it's at least a couple of years away, it could be built upon mature and cost-effective technology rather than being on the cutting edge at the time of release. For instance, a 3nm Zen 5+ architecture could be employed, drawing from established mobile technology that will be accessible at that time. Perhaps the die size and core configuration could be distinctive, with the potential for broader adoption in other handheld devices beyond Deck 2.

RDNA 3 was not as efficient as expected. Sure higher performance but it also needed higher power. Maybe RDNA 4 or 5. Also important is the fact that Valve would try to avoid using any chip based on a new leading edge node. The fact that steam deck is on an older RDNA 2 architecture based on 7nm node is one of the reasons it's so cheap.

It looks to me like Valve's focus is on price and battery life. I think it will try to get something balanced that doesn't necessarily compete with the state-of-the-art AMD APUs. I'd still guess that Valve will release something in the next 2 years, otherwise it will get too far behind what other mobile consoles offer, and the current Deck will struggle in too many games.

So I'd say that it will be newer tech but still low spec. On the CPU side 4 core Zen 4c would likely be a big enough update. On the GPU front AMD still doesn't have anything significantly better than RDNA 2. It will be interesting to see what RDNA 3.5 brings to the table, though RDNA 4 is certainly an option. A custom design with some cache to alleviate the RAM bottleneck might be an option.

considering they got a 6nm shrink on essentially a chip I think only Valve uses.

Yes, this puts them on equal footing with Microsoft and Sony, which implies that the Steam Deck is selling very well.