Read and article that he should be back in 5 - 7 months. Assuming 7 months that puts him back sometime in February. That's about 30 games to play in the regular season. If it takes 48 wins to make the playoffs in the West the W's would need to be at least 28 and 22 record wise and then go 20 and 10 with Klay. Sounds doable.
Now I know it is a different injury, different people, different height and weight, and different sports but Emmanuel Sanders tore his achilles in December and this is a video of him working out. He looks good and close to ready. Hell maybe it is not a foregone conclusion that KD is out all year either.