To begin with, Danny never sell low in his players. Rondo's value is at all time low as he's still recovering from his injury and his stats may look awful to many. Danny won't trade rondo simply for the sake of trading him. If he intends to trade rondo, it will likely be next year's midseason trade deadline, when rondo can play more like his old self and regain his star value throughout the season, like how jordan crawford's value was boosted before getting traded this year.
Besides, trading rondo isn't as easy as you think. Remember when the Kings discussed with Ainge about a trade for rondo using Ben Mclemore, a first round pick plus a filler? Danny was a bit interested in the deal and asked rondo if he would sign with them after his contract expires. Rondo said no and then trade talk stopped since then. Teams won't sacrifice their future for a one year rental. This reflects that rondo has some control in where he'll be traded, while he's likely only willing to be traded to playoff-bound teams, whose first round picks won't be in the lottery and immensely help with our rebuild.
In my opinion, the reason why rondo seems to be playing with so little effort this year is because he has to cautiously deal with his injury. He wouldn't want to turn out to become another rose or westbrook who gets hampered by injuries again when they return. It's of good condition now that rondo is gradually getting back to his old self without risking any injury. And more importantly, I think he's in the tank with Danny.( I know many may argue with this) Rondo, being recognized as one of the highest BBIQ players in the league, how would he not know how to adapt to Brad Steven's ball sharing system. He's still pounding the ball over and over again despite criticisms, and this style of play has no doubt accounted for some of our losses this year. Pressey has excelled by pushing the ball as fast as he can and the team benefited from it. Rondo should know this pretty well but for some reason he decides to do the opposite. These signs showed me that rondo was probably in the tank and trying to help the celts net a higher draft pick this year, which will do good to celtics' future. After naming rondo the captain at the start of the season, i think danny has absolute confidence in Rondo to lead our future and rondo may be very well aware of that , thus don't mind buying into the tank talk.
Yet, my above speculation may just be pure imagination and rondo may have regressed after the ACL injury or simply is not the man we are looking for. I believe Danny will make the right decision in deciding rondo's future in boston, he knows a lot more about rondo than us fans anyway.
According to Ainge, he's gonna enter his first year of prime next year. I don't think it would be wise to let go of a player like that, as he can be a good starting point of a championship team if things go along the 2007 way.