The thing with Carry On films is that the humour fitted the times...but now seem to be a bit dated (not the films...there classic). If they tried to up date it..then it wouldn't be "carry on" if you know what i mean. But if they kept it the same it would feel dated and not soo funny. They should really just learn to leave things alone.
I think that the 'Carry On' films are a success because of the particular talents of the regular characters, Sid James, Kenneth Williams, Hattie Jacques etc. Without these they aren't 'Carry On's. 'Columbus' tried but didn't work. I also agree with the above posts that the most successful fitted with the humour of the times which was suitable to the 'Carry On' approach. 'Carry on London' sounds like a turkey in the making!