While having been confirmed as being in the next three Bond films and also that he will play Q and not R it seems John Cleese isn't too sure about the role beyond that Dark Horizons has reported.
During an interview with TV Week, Clese says: “I wasn’t Brought into the Bond films to replace Desmond but to support him – to be his assistant. I have no idea what my involvement will be with the next Bond film. I don’t expect to know anything until a few weeks before they start filming. That’s how it was With ‘The world is not enough'”.
That said, it seems Cleese hasn't seen the Bond 20 script and knows very few details about Bond 20. You can of course discuss this in the Bond 20 Forums, see you there!