I'm wildly curious, too. My headcanon is that Eve has her eye on the top job and that's why she opted to stay in administration, when she could have gone back to the field. With some years of office experience as Mallory's right hand woman, she'd be a plausible choice. (Also it would fit the tradition of all the previous Ms having the letter M in their real name - the original Fleming one did, Casino Royale established that Dench!M did, Mallory does, so Moneypenny would fit right in, and the original Moneypenny actress, Lois Chilton, once said this was how where she saw her character a few decades later.) Mallory I see as a transitional M. The reason why I doubt they'll go back to the paternalistic model is the choice of Ralph Fiennes, who is the same generation as Daniel Craig is. (It's not like there is a lack of older British actors, if they had wanted to replicate the past.) As to what kind of dynamic they'll have: father-son is out, and James Bond is now in the new position of being the veteran. Mallory will have work at earning everyone's respect at a higher level than "grudging", and that could be interesting, but: I suspect he won't be around for more than two or so films, before moving on the the ministry, while we get a fiftyish female M. And her successor is Eve.

Well , that's my guess for the next four years anyway, or however long till the next film.:)