I think theres a clue in the fact were getting a BD release of Best of Both Worlds One AND Two on the same day they release Season 3.
My money is on CBS-D keeping it in house this time out, at least for 4 and 5. Maybe they'll lease it out again come Season 6 though.
Nope, Season 4 is being done by an external post-house. 5 is being done be CBS-D, perhaps 6 too depending on schedules.