IBM ditched its own PC business -- -- in part because it saw that the PC was becoming a legacy platform, Wladawsky-Berger said.

"We saw this coming, that PCs would become more of a legacy platform where you can still make tons of money but the bulk of the innovation will now happen in the mobile platforms, and tablets and things like that," he said. Luckily, the advances in mobile platforms could apply to PCs and improve them.

"As happened with mainframes, you can integrate those innovations back into the legacy platforms," he said. "Mainframes run Java, mainframes run Linux, mainframes became IP-enabled."

HP said "" in explaining its willingness to leave the PC business.

Still, Wladawsky-Berger said there's no reason to feel sorry for Microsoft. "[Microsoft] will continue to be a gigantic cash generation machine for many years to come. It's just not dominant," he said.