On TBC servers today we have cross faction BG’s which really made playing BG’s fun again as wait times are low all day. Hope this carries on to Wotlk.
Wotlk could see even more people playing Horde for the really powerful PvE racial abilities. Arena focused players will surely have a Ally character for the powerful PvP racial.
For wotlk, having cross faction group finder would make the game so much better and will go a long way in making sure people enjoy playing alts.
Live wow will not have faster xp choices x1/x5/x7 so group finder is how people level … Without cross-faction group finder, I think people would still play on other servers.