Detroit ? Marshall Mathers is ready to get rid of Eminem.

Here’s what it could mean, say those close to the rapper: When he steps off the stage Sept. 17 in Dublin, Ireland, he will have made his final concert appearance. “Encore,” his slyly titled 2004 release, will stand as the final Eminem album. The reign of Eminem, and his alter ego Slim Shady, will have been voluntarily vanquished.

It wouldn’t be a mere name game, in the hip-hop fashion that let Puff Daddy become P. Diddy, or the fanciful indulgence of a superstar toying with personas, like Prince. Nor would it be some gimmicky farewell stunt, say hometown friends and professional associates, many of whom asked not to be named in this story, citing sensitivity about the issue deep within Eminem’s record label and management camps.

What it would represent, say those friends, is a dramatic life shift for a celebrity grown weary of public commotion – and an artist who feels trapped by musical expectations.

“Em has definitely gotten to the level where he feels like he’s accomplished everything he can accomplish in rap,” said rapper Proof, Mathers’ right-hand man onstage. “He wants to kick back and get into the producing thing.”

If Mathers is truly set to shake things up, exactly where he goes from here is unclear. He’s not doing interviews this summer, and his spokesman at Interscope Records in Los Angeles declined to comment. Manager Paul Rosenberg said there’s been “no official decision” about the future. But he acknowledged that some kind of recalibration is likely, adding that Eminem’s latest multi-platinum record is “certainly the cap on this part of his career.”

Such a move by Mathers would shake the tectonic plates of pop culture. At 33, he is now the best-selling hip-hop artist in history and is, by many standards, the globe’s biggest music star.

“Why not bow out while you’re on top?” said Proof, speaking last Friday inside his tour bus at Germain Amphitheater in Columbus, Ohio, second stop on the Anger Management Tour 3.

“Marshall is very smart about this stuff,” said another musical partner. “He knows the danger of being at this level, where there’s nowhere to go but down.”