While I love RO and think it's the best FPS available today, I think it has two factors going against it...
#1: Eastern Front: I hate to say this, but most Americans don't even realize there WAS an Eastern Front, let alone want to play a game about it. My generation has been brainwashed into thinking the Russians were evil monsters. So now we have a game where we can play as either Russians or Germans. Wow, they're both the bad guys! (This is a generalization and I also know that this is not true, but it's the way a LOT of Americans feel). Any WWII game that you want to sell in America and DOESN'T include the Western front, let alone Americans, isn't going to do as well as those that DO. While the Game Engine and Mechanics completely rock, I would like to start seeing British, Italian, and of course American troops hit the game. Variety is what keeps games going for years on end, IMHO.
2. Diffiulty: Let's face it, RO is hard to learn. It's not like the rest of the WWII FPS games, which are all basically clones of each other from a Game Mechanics standpoint. The number of players asking where the crosshair is gives evidence to that. Unfortunately, the fix for this is to make RO more like the rest of the bland and boring WWII FPS's on the Market today. No thanks! I would rather have a smaller community of people who like the way RO is now than a humongus community of bunny hopping l337 Snipor doodz...