I think he is an explosive player and could be a starter somewhere eventually - he just needs to get lucky and find that place. Look at guys all around the league, from Isaiah Thomas to Kemba Walker to John Wall - after a few years in the league, point totals go up and quality of play gets better.
I feel like DJ has what it takes to play, more so than anyone at ND over the last few seasons. But he might get to the point in Boston where he gets too old and expensive for teams to give him a chance. I think he did the right thing playing all 3 years in college (and hope he finishes his degree) but the tendency seems to be for the pro teams to get the kids when they're younger and younger. They might not want to wait until he's 26 or 27 to reach peak. So a trade to a team that needs a solid PG might be a blessing for DJ.
Incidentally, I love DJ's story. He's a perfect example of what Notre Dame can do for someone's life. I'm selfishly pulling for him.