What major storylines or characters have we yet to see completed or finished? Which could possibly be explored in future patches or expansions?
Ozumat, Neptulon, the events that follow the Throne of the Tides.
The Emerald Dream (Rift of Aln still present at the end of Stormrage, possibly hinted at being N'Zoth's doing.)
The old power under Vash'jir.
Azshara's where-abouts and the status of the Naga.
The actual Old Gods (what we have fought was just a small representation of their power)
N'Zoth (Metzen hinted that there was someone paying Deathwing's bills, and Hathen Kraul in Deepholm mentions that Deathwing's minions serve an even greater power)
N'Zoth and Azshara centered expansion. We can explore the rest of the Neptulon storyline, be introduced to Zin-Azshari, explore N'Zoth's titan containment facility, possibly enter the emerald dream, and wrap up the loose ends of N'Zoth. I can see 3 easy raid patches out of that (Azshara, Emerald Dream, N'Zoth) with the possibility of a 4th with some new material.
What are your thoughts? What do you want to see explored? No matte how minor or major it is let it be heard!