End of the Minecraft worlds

So in 1.3 apparently Zombie Pigmen (and ghasts?) will supposedly come out of portals, but it has a rare chance. But there was no note as to the nether "expanding" to 2 endless worlds. It is my theory that yes, this could happen, but I don't think Jeb and the Mojang team are willing to do this, as it would END worlds.

But on to another story. -INSERT HEROBRINE PLOT HERE- (No, just kidding.)

I was walking around in my Minecraft XBOX 360 edition world (THIS IS NOT A HEROBRINE PLOT) and noticed a Desert just sitting there ontop of what might have been an original mountain biome. Brand new world, Minecraft XBOX official release date. I went over there and found the wackiest biome yet. Tons of floating sand, water patches, and a sand mountain that was above the clouds.
I've also found floating islands with 1 or 2 trees on them. Entirely grass or dirt. Again, very high. I walked over and found there was no mountain at all, unknown if there is a crater and it was "pulled" when the world was created. I noticed I believe 2 more. I don't have images, but I know it's rare seed because I found it when I was walking away from a Pink Sheep. This will continue and I will get images soon. -Travis