The Steam Deck leaves little to be desired, especially with the OLED model where Valve made so many small changes that just made it a great device overall.
That being said, a faster SoC would be very welcome, and architectural advancements as well as more modern process nodes would obviously allow for more performance in the same power envelope.
Some games aren’t a great experience on Deck, say Baldur’s Gate 3 in Act 3 especially, or also simply walking through a complex base in Valheim. Zen 5 vs. Zen 2 and RDNA4 vs. RDNA2 on 3nm vs. 6nm should vastly improve things.