I ask this because, obviously, he's the prince of Knowledge. His sphere is information itself. And is this not simply THE most important secret of the TES universe?
Dragonborn clearly shows us that he doesn't know literally everything, and he's constantly hunting new knowledge. And there's no evidence I'm aware of to suggest him having this information, beyond his sphere and nature. But I feel he must be close, and may be nearing this knowledge at this point.
What do you guys think? Would he have some way to find out about the Dreamer?