It's not unrealistic down the road, I suppose, but I don't see it this year or next year.
Since you brought up the future of the celtics, though, I couldn't help but wonder about what will happen after Pierce's retirement and Garnett's first retirement (he will come back mid-season to try to help the Wolves contend in 2015).
The 2014-2015 Celtics will almost certainly feature Rondo, Bradley, and Sullinger. Then there is room for what you have in mind. There will be a major acquisition or two at the SF and C positions- I'm imagining Luol Deng and Andrew Bogut will be strong targets in the long run, owing to their defensive value and what I think will be their price points. The types of players we target, of course, will also depend on how Bradley and Sullinger develop offensively.
2015 will be Rondo's walk year, so I'm betting he will be traded. Who will run the point after rondo, I wonder? What will the trade market look like in two years?