I don't think that going f2p is a sign of failure, so much as it's indicative of the current state of the market. Games like wow and ffxi have very strong and loyal player-bases, so they'll always be profitable from subscriptions. When new games come out, f2p has been an appealing option in the past few years because it's a business strategy to grab a lot of players over a short period of time and perhaps cash-in on microtransactions.