a...Dench is the same M.
If Casino Royale does poorly and the public demands another one from the old continuity, they pretend that this James Bond is recent ex-SAS recruit who shares the SAME name. Alternatively he goes by that alias to protect his original civilian identity because Bond (Connery -> Brosnan - "one" person) had recently retired. This is similar to the old Bond as a codename theory, but not entirely so at the same time.
Thus, the old Bond goes back "into action" if it doesn't work out by having Dench/M call him up or something. Craig could be easily explained off within 5-10 minutes in the next movie.
NOW
b. If the film does well, Craig is accepted by the masses, than we can assume this is truely a reboot, a volume 2 Bond. That Dench's M is another parallel universe M.
Sounds crazy, but it might actually work as insane as it sounds. It's simplier than the code-name idea they thought about back in the "Die Another Day" days. Now of course we should hope for the later scenario, I detest the codename theory - this is a dumbed down "variation" of it.
Edited by Stratus, 12 February 2006 - 12:38 AM.