I have PS Vita and Steam Deck. And while I love the Deck, it's more of a home/travel console for me. It's the Vita that I always carry with me because it's small and light. But sadly looks like major console brands left this market to chinese products.
Also it's possible that Deck 2 will be based on ARM, so it can be again in its own market.
I don't think small handhelds are ever coming back. What happened to smartphone displays has happened to handhelds too.
So what if deck 2 eventually goes arm? Switch 2 *is* arm and it's 8 inches.
Small pocketable handhelds aren't coming back unfortunately.
The future now seems to be if you want something like and portable going XR glasses or possibly steam frame.
Edit: light and portable*
Ps6 is gonna be abandoned like psp and psvita while Sony claims it as a success. Sony are finished