While it’s not out of the realm of possibility, you have to remember that the timekeeper is just one possible guardian referenced once.
Another possibility that I have seen hints at Maya’s soul fusing with the siren’s powers that Ava now has. In DLC 4, the idea is expanded on more by Maya, imprinting onto an echo recorder she gave to Krieg. (just like angel did) It’s also possible that she instinctively imprinted it onto her book when she died.
Some will say that the Maya we meet in DLC4 is just Kreig’s mind, manifesting a memory of what he sees Maya. But some of the dialogue makes me question that. She talks about things I don’t think Krieg would know.
But that is just my opinion.