Plunge in RIM's shares could attract takeover bid

"Jim and Mike are a serious part of the show," said Duncan Stewart, president of Duncan Stewart Asset Management. "It would be tough to do a hostile deal on RIM."

The two men have steered the company from its infancy through its growth stages and into its emergence as one of the best known smartphone manufacturers in the world.

Still, McQueen said, if Microsoft offered the two CEOs several billion dollars for their stake and then asked them to stay on to help continue growing the company's business, "that might be a compelling proposition compared to taking up golf and retiring."

(Reporting by Wojtek Dabrowski; editing by Rob Wilson)