Pep will stay as long as he wants to but also as long as we need him to.
With the CWC and Txiki going it's just about the worse possible time for him to leave. So I think he'll stay, work with Txiki's replacement and stay as long as the club need him to before they identify a replacement.
And I think the club will be as smart as they always are, and look to identify a replacement for Txiki that has either got a proven track record or has worked with the proposed new manager so that transition is also smooth.
Simon Rolfes from Leverkusen coming a year before Xabi Alonso then arrives would be my bet - but only because I think Xabi would be an excellent fit at City.