Rumours of a continuation have swirled since Austin Powers in Goldmember was released in 2002, with Myers apparently signing on to pen another sequel in August.
A source close to the actor has told Page Six that a fourth Austin Powers movie could reach theaters in 2013 at the earliest.
Myers is also writing a musical version of the fictional British superspy's life in hopes of bringing Austin Powers to Broadway.
"Mike would be heavily involved in writing the show, but he will not star in it, even though he has quite a good singing voice," the insider added.
A rep for Myers has declined to comment on the report.
Myers's Austin Powers: International Man of Mystery was a surprise hit when it was released in 1997, taking in more than $67m (£43m) at the box office.
Two further sequels saw Myers star alongside Heather Graham, Beyoncé and Michael Caine.
Myers and second wife Kelly Tisdale welcomed their first child together in September.
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Watch the trailer for Austin Powers in Goldmember below: