Deck 2 to play what? 99% of the current available library on Steam is likely to be handled by the current device (software compatibility issues with Proton aside) so what exactly would they be making it for? It makes no business sense to follow the hardware makers that are only interested in giving you something new each year, only to discard the old thing you had that was perfectly fine.
I don't see Valve releasing a follow up for at least 5 years from launch.
Happy if this post ages badly though. I would like and oled, bigger batter and 120hz