Ainge took over in 03. He promptly traded Antoine Walker, tanked, drafted Al Jeff, Delonte West, Tony Allen, Gerald Green, Ryan Gomes over the next three years then flipped most of them and his lotto pick for KG/Allen. He re-signed Allen a year or two ago so that his contract and KG's ended at the same time. All this isn't just a coincidence. He knew they were getting old and he could make a big play in this year's free agency if he set it up this way. I believe that part of the premise of his pitch to Howard is that he believes he can still retain KG (where is KG going to go? they can still pay him fairly decently and hes a notoriously loyal guy who wants to win). Tell him Rondo/Pierce/KG/Dwight is the core for the next few years, once they leave they'll have a lot of cap space to look for another third banana. As far as media markets is he any better off in Dallas than Boston? Playing with Dirk and Kidd and a whole host of other older players? New Jersey/Brooklyn has appeal but can they retain Deron and if they do is that enough talent to beat the Heat/OKC?
They've got a pretty decent pitch IMO.
Back to the topic though, they're not moving Rondo for anything but a blue chip prospect or another star. Nash could be a nice target in free agency, the chances of signing him are infinitely higher than signing Deron. Unfortunately your only chance of adding a real star in their prime is trading Batum (this is the minimum, as you have little else of value as far as trades for stars go). You could sign Nash and hope Batum does blossom into an all-star. Or maybe you could trade Batum + something for Rondo and still have some money left to burn on a good third core piece.