Well, it really depends on the popularity of the game and how the company manages it. A lot of games will flourish on Free2Play with microtransactions, for example, League of Legends. Not only is it the most popular RTS game for the past few years, it now has championship gaming tournaments for thousands of dollars. As long as the company is clever about creating good new content and cool store items that can be bought, it'll do fairly well. Personally I don't like TERA, but that's just because the battle system just isn't my style.