I have read that his ceiling is that of a starter...not a star, but just a guy that can possibly start in the bigs...
The story on Brett Jackson for the past year or two is that he is a guy who projects as a solid, everyday, regular major league outfielder. He might make an All-Star game in a flukish career year, but that's about it. He isn't a star in the making, he's a pretty good player in the making.
The hype on Brett Jackson is that he is a perennial All-Star.
And unfortunately, more fans believed something closer to the hype than the story.
All that we are seeing in Iowa now is an indication of who Brett Jackson really is.
He's a plus defensive corner outfielder or average defensive center fielder who projects to have 20+ HR power and 20+ SB speed. He has a selectively aggressive approach at the plate that yields a lot of hard hit balls, a lot of strike outs, and a lot of walks.
Currently he is striking out in 31.9% of his at bats for the season, and that number is disturbingly high. He also has a walk rate of 9.7%, the third lowest in any level/season of his career. Despite all that, he still an OPS over .800. In the worst offensive season of his professional life he is still posting solid numbers. That is also an important point, and one we should not over look.
It does appear that he has a hole in swing, and that is something he will need to address. He has time in which to address it, though. The reason the minor league system exists is so players can find their flaws, fix them, and have new flaws exposed. It is possible that this is a flaw he won't be able to fix, but that is by no means certain. He still has plenty of time to make the adjustments he can make.
Realistically, I still suspect Jackson will post a regular major league line in the ballpark of .260/.340/.450 with about 20ish steals and 20ish HR. That's good for an OPS of .790. Those are not All-Star numbers by any means, but they are the numbers of a guy the Cubs can feel reasonably confident about penciling into the No. 7 slot on the lineup card every day for a decade or so (unless he gets passed by someone else out of the system).
I suspect a great deal of the panic over Jackson is that many fans are just now realizing that the hype was ever only just that... hype. And since the false hype was in fact false, they are over reacting and assuming that Jackson is a failed prospect. That's no more accurate than the highly inflated hype.