At the end of every expansion there's always people getting bored and leaving the game: all bosses downed, reputations maxed, friends moving to other games. I'd like to see one or more incentives to keep their accounts active:
1. Title (???)
2. Achievement, "I stuck around and only got this stupid tabard"
3. Special rep allowing slight advantage for leveling in next expansion and/or raid bosses
4. An extra guild reward
5. Other ideas?
I believe something that keeps Blizzard getting more constant income should bring rewards to both players and guilds.
I'd personally say this happened at the end of the last two expansions because Blizzard allowed the final raid of the tier to go on for too long before the next expansion came out. Very simply, if they minimized the amount of time the final raid of this expansion is out before the next expansion so it's not lasting 6+ months, they'd probably save themselves from a lot of players leaving.
Maintain an active sub and log in at least an hour a week, and you get a [Tabard of Azeroth], which when worn will triple your rep with any faction as you complete tasks.
This would give someone the incentive to go after 70 exalted reps and keep the tabard for rep gain in the next expac. So no matter who you just completed the quest for, you get 3x the rep (not XP). Just a thought. I will still grind the 70 reps either way