The Fox musical drama now divides screen-time between the students at McKinley High and the lives of graduates such as Finn (Monteith), Rachel (Lea Michele) and Kurt (Chris Colfer).
"There's still a part of me that's nostalgic [about the old show] for sure," the actor told TVLine. "But all of the possibilities are really exciting."
Monteith also revealed details of his forthcoming comeback to the series, confirming that he will perform Foreigner's 'Juke Box Hero' opposite The Glee Project winner Blake Jenner.
"It was cool, because I felt like I was passing the torch in a sort of awesome way," said the 30-year-old.
"[Blake's character] Ryder inadvertently auditions [for New Directions], and it turns into a fantasy in his head, which explodes into dancing girls, throngs of screaming women in the crowd, and he turns into the 'Juke Box Hero'. He's on drums, and I'm on lead vocals. It's epic."
Glee airs on Thursdays at 9/8c on Fox in the US. In the UK, the fourth season will debut on Sky1 in 2013.
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