With the remaster for Skyrim coming out soon, and Fallout 4 coming out last year, it was kind of expected. Apparently they still have a lot planned for F4.
"To all visitors from Transylvania looking for the head of Voivode Dracula: Yes, we have it. Yes, he's dead. No, you cannot see it. No, he will not return and invade you again. It has been over thirty years, please stop pestering us."
They've dropped like 4-5 full(ish) length DLC's for Fallout 3 and New Vegas. Stands to reason they can do even more with such improved systems and graphics. So yeah, F4 should keep us all satisfied for quite a while.