Ok one thing I have noticed is that during this long periods w/out new content is when players get lost. The sad thing is some of those players will never come back.
With WoWs dev team being the largest it has ever been, I have a idea (kinda pirated from the MMO The Secret World).
How bout monthly content patches. That can be used to tell a story arching us into the next expansion.
Example using WoD
6.0 WoD release, 6.1 would come a month later with 5 new quests telling a story, 6.2 a month after that with 3 quests and a scenario, 6.3 a month after that with 3 new quests and a dungeon, then a month after that 6.4 would be a larger content patch with a new questing zone, raids whatever, but also a few quest to continue that story.
I mean if they did say 10 small content patches, and then 4 major ones I think that would help extend the life of the game. That and with new content coming out monthly or at least close to monthly it would encourage people to stay subbed I would think especially if some of that content was only available for a limited time ala Battlefield Barrens.
I needed to step away from me being annoyed by the no flying on max level toons till 6.1 and came up with this.