The 'returned Abeir' thing was my biggest gripe with the 4e realms. I can live the the Spellplague, and other various changes, but that one bugged me. For one, I'd never read about this twin-world thing in the first place (in either the 2e box set, or the 3e FRCS), nor any of the supplements I own, and for another, why replace Maztica when you've got a huge continent in the southwest of the map that you could use instead.
My homebrewed Realms just put Returned Abeir on that pseudo-Australia in the southwest, and say it was always there, just not really known to many.