It looks like WGE will be AL-legal once they are happy with the final version. Not sure how that will work in practice, however.I have been holding off on buying WGE and GMR until we know if anything in them will be AL legal.
I expect certain segments of the fanbase to have a meltdown if dragonmarks start appearing on the people of the Sword Coast. The alternative would be for the AL to relocate to Eberron for a while; I don't do AL (and I have no idea if that is a viable proposition) but anything that increases the support for Eberron would have my vote.