I've said this for a while, but I'll say it again.
I'm 98% certain a Steam Deck 2 would be ARM based and steam will be working towards getting proton or something similar to work for x86-64 -> ARM. Mainly for battery life gains. I think they've realised that the biggest complaint that people have of the steam deck is that it just does not last long enough when playing higher end games. Getting both a good ARM chipset and an efficient translator will make massive gains.
This news to me almost confirms this theory of mine and they're just also trying to see if the same strategy can work with getting them on people's phones and tablets too.