I will say that it seems likely that the Phoenix is going to end up not replacing Gaea as Thor's mother, but being somehow involved in his birth in a peripheral way. Aaron has dragged this out so much it seems like things are more complicated than they first appear. My prediction is that somehow both Gaea and the Phoenix are going to be Thor's mother somehow. Like somehow Phoenix merged with Gaea or possessed her or was the architect of their union. Or perhaps Gaea was some kind of surrogate mother than carried Thor and birthed him.

cheers,
---the late great Donald Blake