Ryan Seacrest Explains Mysterious 'American Idol' Sign-Off on Series Finale

The longtime host said, "goodnight America. For now." Wait! What?

Seacrest, who hosted the singing competition for all of its 15 seasons, finished by uttering his famous phrase Thursday: "And one more time -- this is so tough -- we say to you from Hollywood, goodnight America."

Then he added mysteriously "for now."

Seacrest, 41, took to Twitter Friday to explain.

"I didn't want to say goodbye last night," he wrote. "Thank you for 15 amazing seasons #IdolFinale."

"There will no doubt be another format or refinement or elevation of the format," he told Billboard. "Now I can actually revamp it and come up with a new version and we can look back on 15 seasons and think of some legitimate ways to allow people to enjoy them again, maybe adding another dimension to it."

Fuller, 55, said that includes working with Pulse, a company that can create "a virtual pop star."