I am, at this very moment, holding a sculpt of a new Eldar Avatar. I am told the Avatar is being looked at to go to production as a plastic kit containing all options. And will be released with the future Eldar Codex. When, you ask? I have been told, "Not for a while." and "When its done."

Specific changes I note:
Does not look like FW version.
Avatar's head is more expressive.
Molten-y look is much more impressive. Bits of fire are evident.
Bloody hand much more bloody...new blood angels may have been an inspiration.
Headdress is more warpstone, elegant, vs current boxey glyph look.
Lots of little details within the armor...it's hard to describe, but its a lot of small detail.
I'm told it will be able to be assembled in various poses, despite the detail.

This one is oversized, so its hard to just scale, but I'd guess he'll be about the same height as a wraithlord, maybe a touch bigger.