Thompson will be able to play in the playoffs, so they have a chance to be in the finals again.
We've seen him injured many times and it does not affect his playing capability, the fact that the Warriors gave him a maximum contract, they know that Thompson will be able to recover easily and will be back healthy to bring the team into the Finals again.
Thanks to modern medicine as Klay said, he can back probably after the All-Star break. That is mid-February so I will assume he will be doing fullcourt drills at early to mid-January. There is a high chance he can play at the playoffs. No need to worries about the possibility of lack of performance as what he just needs to do is to shoot that damn ball. No need to force being an athletic on that part*.
Admit it, if Thompson was not injured last NBA finals, they have a good chance to win even without Durant..
Move on.
"Chances" is still
"chances" even Klay was there.
I doubt they will risk by putting Thompson in playoffs, dude had a serious injury and one of the best defenders in the league, in order to keep his lateral movement going he has to recover really well and I doubt they will have a big chance to win the ring this year so there is no reason to force Klay to come back and play for just 10 games or whatever he can play.
He won't be ready and just out of a new injury with no game shape at all, of course he would be better than any other person they will play but its a risk that is unnecessary if you ask me. Can they do it? Sure. Should they do it? I don't think so. Klay should relax until next season and come back fresh and get his speed up slowly at the start of the season and get better until the end of the season to make a difference in playoffs.
Klay knows what do more than us here. Remember that Klay's main forte' is outside shooting, catch+fake+shoot. As I said above, no need to be pure athletic on that part* if he can't really be like that again once he came back.