f2p would be implemented in a patch or at latest the addon after WoD. Why? Its simple.
After they lose 1.3kk subs down to 8kk 2013, their profit goes down to 90kk Dollar - down from 2xx kk Dollar.
When WoD is finally released at end August - mid September, the subs would be beelding out maybe to 5-6 kk , so 1.5 - 2.5k lesser subs than now.
This would make the profit fall down near zero.
WoD Launch would give some extra money, cus of the -in best case- 2kk sold copys. But it will be like MoP, when MoP released subs climbed up from 9kk to 10,3 k. We all know how much subs are right now, about 7-7,5kk , near 3 million losses. The subs will go maybe up again to 7kk, but after few months it goes down, like it goes down since WotLK. It will not take so long when they hit the 5kk subs, and they have to reduce turnover much to be profit with 5kk subs.
Why do u think they said at blizzcon they want to release every year a new expac? Cus they knew that the subs will be falling down to the point where there is no profit - and this is the main reason for a joint-stock company.
The game is getting really old, there are every few months new MMOs who maybe are not the size as WoW is, but enough to lure some bored and weary wow players to try it. Maybe for few months, maybe forever (=they are not coming back to wow).
If Wildstar and Eso and Destiny only get 2kk WOW Players, which is not exaggerated much, what do u think would happen if at this time the subs go down to 4kk..