Who knows what Mendes has in mind. I would not count him out before knowing what he wants to do with a new actor.
Mind you, at first he thought casting Craig was a mistake. Sure, he has come around on that. But I would be interested to see how Mendes would mold a Bond he actually had in mind.
And therein lies the problem as far as I'm concerned, SAF. Mendes has been tooting his own horn for years about how he was responsible for the death of Dench's M ("you have to make it personal"), choosing Fiennes as her replacement, reintroducing and casting Q and Moneypenny, and insisting that the DB5 match it's Goldfinger counterpart despite the inherent inconsistency (the latter couple of these could be seen as a subtle stripping of the reboot concept entirely). And let's not forget that it was likely Mendes' decision to portray Bond as an "old dog" trying to find his place in the world in Skyfall, despite the fact that he was essentially a relative rookie (at least to the 00-section) in the previous film. And then the brilliant ( 
) decision to reintroduce Blofeld, only this time in the guise of Bond's foster brother and childhood nemesis (after all, "it must resonate on a personal level")-- I feel like Mendes would be tooting his own horn for this as well, had fan response not been so negative. Oh, and his DB5 fetish apparently knows no bounds, resulting in the car's perplexing return in SP, negating the symbolism and impact of its destruction in SF. And enough with the homages-- at this point, they are no longer "fan service," but rather "self service."
What I'm getting at is this: it seems as if Mendes is solely making big changes to the franchise because he wants to be the one to make them, as if he is desperately trying to "leave his mark" on the franchise. Way too many of his decisions undid so much of the good in CR and QoS (why does it come across as if he completely jettisoned the reboot idea?). And way too many pivotal moments in Bond's life occurred in the span of just two films (being shot by Moneypenny and going off the grid; TWO explosions at the Vauxhall Cross building; death of Dench's M; new M, Q, and Moneypenny; discovering that his enemy this entire time has been his long dead foster brother named Blofeld; potentially leaving the service for the new love of his life). All of this (combined with the incessant homages) reeks of self-aggrandizement.
Notwithstanding the constant criticism on this site and others, at least Glen did not feel the need to spice things up with every Bond movie in the 80s (granted, Cubby probably wouldn't have let him even had he wanted to), and we got a solid run of films out of him (both Octopussy and The Living Daylights are in my top 5).
So to respond to your point, Secret Agent Fan, the last thing I want is to see how Mendes would approach his Bond. He has already left his mark on the franchise. Time for some fresh blood in the director's chair.
Just to be clear: I love Fiennes, Harris, and Whishaw. I hope all three stay on for many years to come. And I also really like both Skyfall and SPECTRE, so please do not take any of my above comments to indicate otherwise-- I was highlighting my legitimate reservations with Mendes, although I concede that there is much to love in both of his films.
I just think that the series needs to move away from some of the baggage which has been plaguing it recently, and I think the best way to do that is to hire a competent director who does not feel the need to leave his mark on the franchise. More emphasis on a strong and engaging plot could do wonders for the franchise.
