If Ainge doesn't trade the pick at the deadline, I don't think he trades it this June either.
The names many have mentioned, like PG13 and Cousins, become Free Agents after NEXT season (PG13 has a player option I believe so he will opt-out).
Give up a top-2 pick for a one year rental without a long term commitment? Doubt it. And Jimmy Butler is the exception because his contract runs through 2019.. but I don't think he's worth the price they will command (Nets Pick + Smart/Bradley + Future non-Brooklyn Picks + Zeller/Amir).