"Yes, I'll be back," said Monteith, who plays Finn Hudson, at Fox's Television Critics Association winter press tour in Pasadena Jan. 8. "I'm very excited," said Colfer, who plays Kurt Hummel and confirmed his return with TheInsider.com.

Although the characters played by Monteith, Michele and Colfer will graduate from McKinley High at the end of the current season, Reilly said that the "Glee" team has come up with an "interesting idea that [will] give us something cool to dig into for next season."

As previously reported, producer Ryan Murphy talked last year about the possibility of a "Glee" spin-off in which the three McKinley grads would pursue their dreams at New York City's Julliard School. Plans were shortly put on hold.

"Ryan has come up with a brilliant, ground-breaking idea for how to include us graduating high school seniors into next season and it's really exciting," said Michele. "We don't want to give away the new formula but I'm excited and Cory is so excited to be coming back next year. When we heard Ryan's plan, it really made us even more thrilled."

As for the "Glee" underclassmen, Grant Gustin, who plays Warbler Sebastian Smythe, has been offered to become a series regular on the fourth season.

Gustin, who plays a gay student at Dalton Academy that tries to come between Kurt and Blaine (Colfer and How to Succeed's Darren Criss, respectively), said that he will be "in and out" of episodes in the current season and that an offer for a series regular remains "on the table." He will be seen next in the Michael Jackson tribute episode.

"Glee" airs Tuesday nights on Fox at 8 PM ET.