World of Warcraft is 9 years old, which is 1012 in MMO years. The old thing still has its wits about it, but in its dotage, we're going to start seeing more changes like patch 5.4's 'Connected Realms' functionality.
Expanding on existing tech, this will link servers together so that players on less populated servers can play with those from other servers without having to migrate their characters.
The system will allow players on different servers to share auction houses, raids, and to do quest together. It's a less disruptive alternative to closing and merging servers, which tends to lead to players losing a part of their identity, with the added debuff of making your MMO look like it's dipping in popularity. Ahem. Blizzard were careful not to say that when they first announced the feature back in August.
World of Warcraft is still absurdly healthy by subscription MMO standards, with more expansions to come, so let's not start the eulogies just yet. A list of the connect WoW realms is available over at the devblog.