This might go without saying but we are reaching a pretty critical month or two for Kemba. I think Danny was right on when he said "this season will tell us a lot".
Many NBA players have knee issues, meniscus surgery, arthritis, etc and still are able to compete at a high level..... sometimes. The docs know what his knee looks like but still probably don't know exactly how he will respond to the injections, time off, and rehab.
Unfortunately, the longer you go without being particularly good, the higher the chances we are reaching the end of the road for a return to something close All-Star level play. We have to account for the rust factor and trying to get back up to speed, but now that those first few weeks are out the way, we should get a good picture where he really is over the next month or two.
Once you start getting into 1+ year of poor play and sitting out due to arthritis on the wrong wide of 30, then it starts to really look dire (see: Blake Griffin).