Dooling wasn't a priority, but that doesn't mean he won't return. As was mentioned, they may have held off on him a bit in case they needed him in a S&T, but since we seem to be set in that regard now I wouldn't be surprised to see him come back. He wasn't great for most of the season, but he'd be coming back to provide depth and some mentorship to Rondo (he seems like one of the only guys Rondo listens to).
Most of the backup PG duties will be handled by JET and AB, but we could still use someone else on the bench (especially with Moore gone), and we don't have much money left to spend.
But, the fact that he hasn't re-signed yet, it's still only mid-July. I wouldn't over-interpret that.