We caught up with the "8 Mile" star shortly after the classic film marked its 20th anniversary ... and we had to ask if there was anything in the works for a new story related to the OG characters.

Mekhi tells TMZ Hip Hop ... there will never be a follow-up to the film, as far as he's concerned. He says, sometimes it's best to leave the classics alone ... adding there's never been any convo about making one happen.

Now, he does acknowledge a sequel could be interesting -- just story-wise -- but he says he wouldn't want to be in it, and he doubts his costar Eminem would be a part of it either.

As far as their relationship goes ... he says they're still pals and they keep in touch. He adds, Em is focusing more on his music right now, so that's another reason they won't be returning to 8 Mile Road.

Since the film dropped in November 2002, Eminem's music career's had its ups and downs, but he's still widely recognized as a hip hop icon ... and he was inducted into the Rock & Roll Hall of Fame this year.