ScotAirways use the D328, rather than larger aircraft, as they claim to prefer offering more frequent flights on smaller aircraft. As I understand, they are not currently looking into acquiring larger aircraft types, or jets.
I believe that ScotAirways are continually on the lookout for new scheduled routes, but clearly do not feel there are any others they want to 'risk' at present. It seems that of the fleet of eight aircraft is well utilised, as although CB only operate three scheduled routes, a considerable number of corporate charters are operated for various companies and organisations, as I believe a previous poster has already mentioned.
Leon