Is there a end to any mmo

Some MMOs have story lines which you can complete along with side quests (potentially repeatable). If you finish the story, you can argue that you saw the end of the game.
Even if the game does not offer a distinct story line, finishing EVERY SINGLE one of the quests available from the game you can arguably, based on how you look at things, say you have finished the game. There are more things to do like finding better loot or grinding to reach the level cap, but generally you have no more entertainment or excitement you can get from the game.

Due to the openness of the game, many MMO developers update their games with additional contents to keep players coming back for more.

The idea is: Is there a point where there is ABSOLUTELY NOTHING to do? (ex. 'beating' the game)-Not really; but it does not give you infinite hours of play time either. At some point, you just get bored of it, find a new game, or just finish all the quests and reach the level cap and aren't much excitements left.

I hope this answer helped.