Johnson is a kid and has been to 37 schools while he's played. He's as fickle as the rest of them, probably more so. You can't trust the kid. It's possible he'll be gone before the end of the season. With him, anything is possible. He could say he's staying at Pitt, be part of summer practices, and be gone before the season starts if he doesn't get what he wants.
With the other factors:
1) There is no guarantee that Hugley will be here next year and it is just as likely he won't be here.
2) There is no guarantee that Pitt will make any tournament this year. NIT is more likely, but that's not even guaranteed. NCAAT is a tall order at this point, looking at their schedule. They'd have to at least win 6 of their remaining games then a game or 2 in the ACCT to be considered for the NCAAT. So no guarantees.
3) I think Fede is more of an enticement that the twins, but the twins may turn out decent.
There's a lot of work to be done on this team before we can say they have the makeup to be a decent team next year. I'm not sure Johnson wants to play on a team that won't give him a chance to showcase his talents, especially in post-season tournaments. He has only one objective: to go pro ASAP. He's just as likely to do that next year as he is to play college ball somewhere. With him, I'd never count on anything beyond what he does today.