I believe Tatum has MVP level potential. I think he can develop into that kind of unstoppable offensive force that Kevin Durant has been for years. The kind of guy we saw from late-January through to his shoulder injury: 28/7/5 on 49/39/87 shooting, or thereabouts.
We saw some playmaking development from Brown last season, and if he can carry that on and follow the Jimmy Butler path of developing into a strong passer, his potential is high. I don't see him reaching Butler's level, but there's room for improvement.
I think Smart is who he is. 28 years old, coming off a career best year. The only hope would be more careful shot-selection like we saw in 18-19.
Rob might nearly be 25, but I still think there are some levels to be unlocked. His free throw shooting made a significant jump, and I think his passing has the potential to be like Al's is.
Grant is near his ceiling for me, chiefly because he is both athletically limited nor skilful with ball-in-hand (i.e., his woeful dribbling). Some passing improvement would be nice, but it's regressed each season.
White and Brogdon are both who they are. White could shoot better, but I think we know what both provides.
I am still fully confident Pritchard can be for us what Mills was for San Antonio. Especially with his improving defence.