Not surprising at all. In the thread talking about potential Rondo destinations, Dallas was the first thing that came to my mind.
They're in the market to make big splashes, and with CP3 a lock with the Clippers already, who else do they go? Jennings, Tyreke, Teague, Vasquez, and Harris are all available among others, but Rondo is head and shoulders above all of them.
They have Marion's expiring, they can offer future firsts, they drafted a young PG in Larkin a few nights ago, and they have plenty of cap space to offer a trade exception.
I don't know if Ainge wants to deal Rondo with his trade value depressed due to his injury (or if ever), but Dallas would be one of the more sensible trade partners.