As far as I know, Cambridge has no ambition to establish Class D airspace.
Last I heard (and as a then councillor I did get invited to things that weren't open to the public) they were, in fact, thinking about it. But that was over a year ago, and there have been several changes of airline using the airport since then, or at least that's what it feels like, and the views may change with the customers.
Thanks for posting this. That is interesting:I hadn't realised.
I think the basic point remains though: in order for them to want class D, they would need a volume of commercial traffic sufficient to justify employing sufficient radar controllers to man the radar during all opening hours; and I can't see that happening at current levels.