Edit: Beaten to the punch.

I posted this in the other thread, but I'll mention it here as well.

The developers have just finally had the chance to take a break (i.e. short vacation) since the release of Heavensward. We can't just chain them to their desks and let their brains fry. They need rest too.

Although patch 3.1 will be late, all subsequent patches will be on the regular 3 month interval schedule.