Anything is possible, but I think there would have to be a significant injury to the Celtics (or maybe some other team) that would force either team involved in the trade to be a bit desperate.
On paper, the Celtics are pretty set going into this season, though I'm sure they'd love to upgrade the higher end of the roster even if it meant sacrificing some depth.
The problem I see that is our most valuable trade pieces are Rondo, Bradley, Green, and, if he has a good start to the year, Sullinger.
Rondo is a cornerstone, so the trade would have to be a major upgrade (e.g. Chris Paul) to be worthwhile, and I don't think there are any names out there likely to be traded this year of that caliber. Green could up his value with a really bounce-back year coming off heart surgery, but his contract is likely to look fairly untradable for a while. As for Bradley and Sullinger, they'd have to be combined with some bigger contracts to be traded for anybody significant, and that again would implicate somebody like Rondo, Pierce, or Garnett.
I think it's possible a smaller trade could happen involving, some combination of Courtney Lee, Bradley, and / or Sullinger (or perhaps Jeff Green if he really looks great to start he year).
Still, I think Danny will probably stand pat unless somebody suffers a major injury (e.g. Terry or Bass is out for the year).
Anyway, the only trade possibilities I can think of are Big Al and Josh Smith, both of whom could fit next to KG and be a major upgrade for us in the rebounding and interior scoring department. Both could also be available well before mid-season. But the cost would probably be pretty high.