I dont think they would lose money if they made it into an MMO. Actually i'm pretty sure they would make MUCH MUCH MUCH more money if they charged to play it.
WoW got 8 Million users online. Now each user pays $15 a month. 15 x 12 = $180 a year. 8,000,000 x 15 = $120,000,000 a year. Now lets say the game was $30. 30 x 8,000,000 = $240,000,000. The game has been out for about 3 Years. So their total income made off of just
WoW is $600,000,000. That's including the pay to play charge and the game cost charge. Think about it? They really wouldn't lose anything, they would make so much more.