I hope Notch won't add this. I mean it's awesome, but is should stay as a mod for people who like it.
I don't understand why people say things like this. If Notch does add it, people who don't want the Aether in their game don't have to build the portal. If there's a portal on their server, they don't have to enter it.
Having 3 alternate dimensions sounds redundant, and the name of the new dimension makes it even so.
Otherwise good mod.
I actually like that thought. Nether for nether stuff, aether for aether stuff (since the mod is introducing a lot of new stuff in that area), and the normal sky dimension which is normal world except with floating islands. I'd like that variety.