There's also the DV detail that Ammorachius is the only Sword that has not been periodically remade/reforged, and also is the one we know was previously in the keeping of a ridiculously powerful wizard.
I suspect a reforging of the Blades will happen, and the "How did Merlin do It?" question will be important.
I dont really think, or at least dont really want, Demonreach to be Avalon. I dont mind the world being big enough for two magic Islands, and I kinda think it cheapens Avalon to say Merlin Created it the way he did Demonreach. Id rather it be out there (maybe a NN place, maybe a earth island) and serve another specific function the way the Well does.
There are a number of longstanding theories that equates Mab and Maeve to some of the Queens by the historic etymology of their names, and various ties to the old myths. Elaine too. Im not sure how much stock I put into that, if only because Ive seen that same body of source material be used sooooo many different ways.