Realistically it will take us 3-4 seasons AT LEAST to get back to being a perennial 50+ win team. By that time, Rondo will be in his early 30s and a lot of the athleticism that allows him to take over games at times (speed, agility, skying for rebounds etc) will be gone.
As others have said, it's probably in the interests of both parties to trade Rondo for a sub-25 year old prospect once he plays his way back from the injury and restores his trade value.