Heya. So recently we've had a lot of once successful pay-to-play MMORPGs change to a free-to-play business model. Naturally, you can and are expected to still pay, but you are not forced to do so. You might enjoy various benefits, such as more content being available to you or exclusive perks. After games like DDO, LOTR and just recently PoBS it seems to be an increasing trend of a swap in business models. The old "pay your 15 bucks a month" method might not be as competitive anymore as it used to be.
Of course the question is, which games are going down the same route in the future? There are many candidates, but my top pick would have to be Vanguard.
Vanguard, huh? Many of you might not remember it. I don't even expect many people to have heard of it, as unfortunately this game did neither have good marketing nor a very large playerbase to spread the word. With all the problems the game had at its launch it was to be expected that many subscribers wouldn't be staying for long.