The Soul Cairn can be revisted so Valerica can be talked to so she can return to Tamriel.
The new bird meshes are fleshless: There are literally bone birds flying around Castle Volkihar.
Durnehviir can be summoned in Sovngarde during the main quest. Talk about meeting Alduin in the hood...
Gelebor is over 3000 years old. For an elf, that is more than Neloth.