depends on the update. if new classes, new items, and new dungeons / maps, then maybe. you do know that the reason a MMO dies is because of lack of updates right? most classic MMOs are still up and running because they are continuously being updated. newer MMO like war of angels have been deserted by players because it has never been updated which eventually lead to the server being closed.
I think I would go back and play the game again, depending on the update as poringslasher has said. I might check it out if there was a bug before or something like that and the gamemakers have fixed that certain bug.
i have tried many MMOs before, i have left a lot too. but whenever a major update has been released, i tend to check out that game again, especially if new skills and items are introduced.