I absolutely love JJ, he is very good on the boards, athletic, has improved on both ends of the floor and like you said is only 23.
I would much rather have him than BB, in fact I'd rather have him than Ilysova. However he will be too expensive and I can't see a scenario where Portland let's him walk, they will at least sign and trade him. He would probably command at least 7-8 mill a year for 3-4 years