The new service to Keflavik should do well. EasyJet have seen large numbers of passengers using their other 4 services to Iceland, most of them filling the larger A320s. Add this to the fact that in general tourism in Iceland is getting bigger and bigger each year. It is interesting that BFS can now offer a scheduled service that no other airport on the island of Ireland can, so hopefully this will bring customers up over the border.
Incidently, winter in Iceland is very popular for Northern Lights themed trips- even if it is bl00dy freezing! Jet2 have operated the occasional charter in the past, aswell as Icelandair out of Dublin, both at much higher prices. Hopefully 2 flights a week over the middle of the winter will work out well for them