Once upon a time, Charlie Giancarlo was Cisco's crown prince, the heir certain to CEO John Chambers. As chief development officer, he oversaw a vast swathe of future products. But his power was recently cut back, with R&D responsibilities handed over to a council of executives. Now Giancarlo has resigned, and he's joining Silver Lake Partners, the tech-buyout fund. Not for long, though, we'd bet. Private-equity funds like Silver Lake and Elevation Partners are proving convenient places to park CEOs-in-waiting. Think of Giancarlo's career move as a temporary exile as he searches for a new kingdom.