I think Steam OS is going to become a default OS for handhelds (aside from Nintendo).
What are the next steps?
1) More native Linux games.
2) Moving to ARM architecture.
imo neither one.
native linux ports (historically by Feral Interactive or Aspyr) often perform a lot worse than windows w/ proton, and have more quirky problems with sound, windowing, and controller support. it doesn't have to be this way, but in 99% of cases, devs treat the linux port as a low priority. we'd get more bang for the buck if devs
adopted vulkan on windows, which can be translated on linux with barely any performance penalty.
arm... i just don't see it. even with the benefits of battery life and thermals, would you want to take the performance hit of x86 emulation in every game before 2025? until arm is widely supported on desktop, i don't think it's a good handheld pc option.
the obvious next step is just anticheat. get to the point where "Steam Verified" isn't necessary because every game works. not having games like call of duty and fortnite on the deck is the biggest knock against it.