Reddit has come up with a theory that John Bennett was behind the bust on Cesar where all of Aleida’s children and Daya and Bennett’s new baby are taken into custody. In both the scene where Bennett visits Cesar and the scene where they are busted, Cesar’s girlfriend shouts that a “white boy/guy is here to see you.” This parallel seemingly suggests that Bennett is connected with the bust.
I believe that Bennett’s proposal to Daya was his way of solidifying the situation before he left. I also think that Bennett will be showing up midway through season 4, months after his employment at Litchfield to claim the baby as his own and to take care of Daya, as he promised her he would. I think Bennett decided to remove himself from his situation without giving anyone a head’s up, for when he sees Daya, he is unable to think of plausible options regarding their conundrum. The easiest way to separate himself from the illegality of their relationship and his catastrophic decision making skills was to remove himself from the situation entirely, and then return when he is sure that their future together is sealed.