The bassist posted a teaser tweet to fans, suggesting he could be joining the current GNR's line-up on tour in South America.
He wrote: "Argentina, Paraguay, Bolivia, Brazil! See y'all in the next few weeks, Si (yes)? GNR."
The announcement, which came on the eve of April Fools' Day, makes sense for fans of GNR as Rose's current bass player, Tommy Stinson, is preparing for a reunion of his own with the Replacements at the upcoming Coachella festival.
According to the tweet, McKagan will join the tour in Buenos Aires for a show on April 6.
The bassist quit Guns N' Roses in 1997. He was inducted into the Rock & Roll Hall of Fame as a member of the band in 2012.