Depends entirely on Danny's success in recruiting FAs. If they can't use their cap space, they'll keep him -- which I assume has been the plan all along.
The problem with this thinking pattern is that Danny has only 2 days to make that type of decision (2 days in which only verbal agreements can be made), and I very much doubt that in 2 days Danny will have exhausted, or even made his minimal due diligence, to properly analyze market opportunities.
The smart play is simply to renounce Johnson, and if nothing shakes up, then try to sign him once again if he's still available. If we lose him, we lose him, and we move on. Not a big loss. I'd rather Ainge has all the advantages he can get in the free-agency market rather than hinder him with a $12 Million contract.