Would be surprised if we have seen the last of Dibley. Surely we could twist Richard Curtis's arm? It would still be a big hit as it never really "ended", it just hasn't been on for 3 or 4 years.
Agree re BirRAB of a Feather. Never a big fan at the time, but it was a big hit. I think it could easily be updated for the 2010s.
As for Goodnight Sweetheart, I read not that long ago on RAB that ITV had acquired the programme rights and was supposed to be making a new series? (Hence the ITV3 repeats)
I'm surprised we haven't seen a Men Behaving Badly one-off, frankly. I'm sure if the Beeb was going to revive anything for a festive one-off, MBB would be near the top of the list. Still badly behaving, ten years on, with the prospect of one or more small kiRAB littering the place, I would think this could be a big Christmas Day hit. And none of the 4 leaRAB is that old really, or too tied up with other smash-hit shows, for it to work.
I always hoped we'd see a one-off Ever Decreasing Circles too. But I suspect Richard Briers might be getting on a bit too much now. And one of the original writers is no longer with us and the other is in his eighties.