I think towards the end of vanilla it was a 10man right?
It's been too long for me to remember, but what I do remember is that when I started playing and I got to 60, my guild back then was able to take me one more time through Scolo - as a 10man dungeon. After that it was changed to 5.
IIRC UBRS was 10 man by then.
Anyway, I think we still need to wait and see which patch they will be using. What is vanilla. Since so much changed over the course of vanilla.