Guild Wars 2

And if not, will it roll around next year?

It is highly plausible.

Have there been other events that became permanent?

The dev for SAB has said that its for the month of April only, for now. They are building out the next world, and it won’t be next month for sure.

I assume that the SAB will open new zones or worlds when they have time. Look at dev posts and you will see that it is something they will keep building. Many posts on it in other threads.

It has been stated numerous times that it is a April only event, and the question of re-apperences and even additional content will be based us the player community’s response.

As of right now, it’s not looking that way. It has been posted that it is for the month of April only. Now, what I do think is going to happen, I think it’s likely to become a monthly event every April. Probably with expansions every year. That’s my personal prediction. Based on the facts that:

-One, we’ve not saved the princess and thus not completed the story.
-Two, There’s still a ton more between stages map yet unexplored.
-Three, the three unaccessible doors in the lobby (the place where you go after giving your coin to Moto, with the central fountain, and where you choose infantile mode and such).