Pierce and KG are givens.
Rondo will be signed to an extension ASAP; I suspect they'll try and lock up Powe to an extension as soon as they can, as well.
House will leave; someone will FINALLY offer him a multi-year contract, I'm going to predict. Posey, I bet will resign, it's a great situation for him here and he fits into what they're doing pertfectly.
Tony Allen is gone. He's still making dumb rookie mistakes what, four years into his career? It's not like he was drafted as a high school kid; if he hasn't developed any consistency at this point of his career, will he ever?
BBD will be traded; Powe's locked down the backup PF spot for the foreseeable future, and they've got to be concerned that he's Oliver Miller II. Trade him now while he's got value, rather than watch him sit on the bench next season.
The real question - the one that's hardest to anticipate - is what happens with Ray Allen. He's an expiring contract in another year; will they resign him, let him walk after '10, or trade him in the summer of 2009? A lot depends, I think, on how he performs next year; he's clearly the one of the big three who's had the most difficult transition, and seems to be showing his age more than the others. They MAY decide, depending on how much improvement Rondo shows next year (and how much HIS extension will command) that the new big three is Pierce, KG, Rondo, and let Ray Allen walk in 2010 rather than make a trade and commit to MORE salary.
But, otherwise I suspect that this basic core is our team for the next couple years. They'll bring in someone else to play backup PG next year, and maybe another wing and another big man for the bench - but I suspect Danny will be a lot less active at least on the trade front than in previous years.