The games go to F2P model when the number of subscriptions down to less 200k as a desperate action for non shut down the servers.

TERA, RIFT, AION, SWTOR etc.

When your game have over 1.8 million of active subscriptions and 500k of players logging everyday, it is not necessary go to F2P model....

Personally i wish to see survey asking. "Do you want see more content for 16/24 men raids"?