Yeah anything is possible.Kessler has hands that Gobert can only dream about. But I'm not sure how much more he can develop offensively. His jump shot looks decent like it has some potential though. I mean look at Malone's rookie year from the FT and jump shooting in general.
Gobert is an all time offensive player though. I don't think WK can baby hook his way to being a better offensive player than Gobert. Plus there's the issue that WK probably won't ever develop the ability to get to the ft line that Gobert did. So in my estimation for WK to be a better offensive player than Gobert he will need to be a 75%+ ft shooter and be 60% plus from the floor with a shot diet that exist outside of 5 feet.
The best thing you can say about WK over Gobert offensively is that he is more trustworthy with the ball in tight spaces.