@Omedon
Let me explain you how "this" works:
The launch sales of a WoW expansion are already good enough to make profit for the company.
Stay subbed for a couple more months? Wel...even better! A couple more profits!
1 year passes
It is no longer profitable to keep making new content
After this time....Blizzard no longer gives a crap about this game.
The profits were already made at this point.
Only a minority stay subbed at this point.
1+1=2
TLDR:
Blizzard only needs YOU to buy the expansion and stay subbed a couple months.
If you do more than that? Great, Blizzard happy...but...they dont care about YOU enough to keep making new content after 1.5 year