I just dont' see the point of getting rid of a 25 year old all-star when you're trying to rebuild.
You want to have 25 year old all-stars on your team when you're assembling a new core to your team. Getting rid of him for the sake of draft position is just hitting the reset button because you lack the vision to try something else.
One 25 year old all star (who isn't a top five player in the game) is going to make your team good enough to just make the playoffs or just miss the playoffs. That isn't a good place to be when you are trying to rebuild. You won't be bad enough to get the truly elite draft assets and likewise won't be good enough to draw elite level players to your team. You end up with overpriced role players in free agency.
We've been over this before and I'm still not convinced.
If Rondo is as limited as you seem to think I fail to see why we won't be bad enough to get decent picks anyways. If the very picks you seem to think are the foundation would produce a player as good as Rondo is right now we'd be estatic. So why throw away a player in hand outright?
The Kings, Warriors, Bobcats, Clippers, etc. were all repeat lottery bound teams that basically never got anywhere. Better to try and build with Rondo than just punt and say to the fan base "Sorry we're going to dump a 25 year old high level player so we can be as terrible as possible for four years."
This isn't dumping Gerald Wallace and Stephen Jackson, or dumping Camby and Wallace again, etc..
Rondo is a good player, he is just inconsistent, but when he is on he is a great player.
As for the rest if you are truly bad it is rare you are going to get an elite talent from day 1 (the only 3 that fit that bill in the last 20 years or so are Lebron, Shaq and Duncan and the first two teams were in the lottery again after), thus you will be in a position to collect three or four very good players while they develop and can form the core of your next contending team. If you draft well, you should get at least two (and really should get three) players worth building around.
A guy like Rondo will keep the Celtics as a 30 win team, which means they would have to get very lucky in the lottery, to get a top three talent. If the Celtics move Rondo, they will likely get a lottery pick or a recent lottery pick (plus the two picks in the 20's). In addition, that team will be pretty bad and will get a very high pick in the 2013 draft and will have a ton of cap space where they might be able to draw two top tier talents to pair with the two lottery picks. I just don't see Rondo as being enough to draw another star, whereas two high end players and the room for two top tier free agents, might be a draw.