I know this post is a little early (game 3 against Houston is tonight) but I've been thinking about how the jazz can improve next season. The biggest opportunity is probably free agency, which deserves its own post. The next biggest chance to improve will likely come from Mitchell. Mitchell had a historically great rookie year and the changes he makes during the offseason will give us an indication of how good he can become.
To over simplify, Mitchell's future seasons can be better, about the same, or worse than his rookie campaign. I don't imagine he'll get worse so I'm ignoring that option. If he stays the same, the jazz have a terrific playmaker who will likely make a few all-star teams before retiring (probably similar to Lillard, not bad but probably not winning a title as the team's best player). If he gets better, the jazz likely have a perennial all-star and all-NBA player.
So how can Mitchell get better? I wish I had time to look at the data on this, but I assume most players who go from irregular all-star to perennial all-star do so by some combination of increased usage rate or efficiency. Mitchell's usage rate is already really high, 29.1 (#18 in the league), especially for a rookie (#6 all time of rookies with at least 50 games).
He usage rate can, and probably should, go up next year but he's not likely to make a big jump. Wade (who I think it Mitchell's best possible comp) had a usage rate during his pre-Lebron years between 32-36. Most elite players this season seemed to have usage rates between 29 and 32, with Harden, Westbrook, and Embiid being the exceptions with higher rates. So Mitchell will probably have higher usage rates over his next 8 seasons, but not drastically so (especially with Snyder's system). I don't know if a slight increase in usage will be enough for Mitchell to make the leap to elite.
This leaves efficiency. He's an okay 3-point shooter (34%) but has a lot of room to improve (ranked #69 of guards with at least 50 games, slightly ahead of Rondo). His overall FG%, eFG%, and TS% are average for a guard (44%, 51%, 54% respectively) so there's lots of room for improvement here. Shooting is generally hard for rookies (outside shooting especially) so I expect he'll improve over the next few years.
His 3-point and FT rates (.404, .218) can definitely improve. His FTA are high for a guard (3.8, #14) but needs to improve (the guards ahead of him are generally considered best in the league). More experience on drawing fouls and respect from the refs should get his FTA closer to 6 (hopefully he learns some, but not too much, from Paul and Harden this series). Snyder's egalitarian system will probably keep Mitchell from being in the top-5 FTA for guards but that's okay.
Watching Mitchell around the basket is a lot of fun. His ability to get up (and make) shots in traffic is incredible but his ability to avoid defenders is probably keeping him from drawing fouls.