I'd argue that it's not a series that needs to do that, and that's the problem/brilliant thing about novels - they're not (usually) "licences" for companies to own and exploit. It's only when they get sold on to make movies and things that they become money-trees.
We're also not sure about the mechanics of this deal - did Penguin approach DA's widow (whose name I can't remember) with the possibility of making another book, or did she think of it and suggest Colfer? Did
she suggest Colfer, or does her involvement equal her saying "ooh, he's a good choice" and nothing else? Some scenarios there are better than others.
I am against the Colfer-haters, though. At no point of this debacle is his writing at fault.
If Douglas Adam's widow said to you, "want to write a new Hitchiker's book?" would you say no?
I have been thinking about this, and from the position I'm in now (struggling writer but one with absolutely zero chance of getting this offer) I wouldn't, because the fans don't really want it and I don't think I could do his legacy justice in this regard.
On the other hand, if the offer did
genuinely land in my lap, would I say say no? Theoretically I'd like to say that I'd still say no, but in practice if it really happened... it depends if my desire to become a famous writer managed to overpower my morals.
However, what I wouldn't
say no to is that third Dirk Gently series, or even finishing The Salmon of Doubt
as a novel. There's enough of a start there to make an interesting challenge. I'd compare that one to being a substitute teacher - the kids have been taught a lot and the lesson plan's available, it'd just be my job to make the little buggers sit down and do the work.