Copenhagen
Always thought this was the case, Ryanair would move it to STN, once easyJet pull out.
I would suspect Ryanair will keep the route for the summer, but highly doubt it will still be operating come the winter.
As the STN route is only operating three times daily, it not practical to move LTN passengers to the STN route.
easyJet and Ryanair originally chose to operate the Copenhagen route from Luton in the first instance, as Danish airport were offering massive incentives to LCC's to start new routes which were not previously served from there. So hence they both went for the LTN market, as LHR, LGW and STN were being served.
I'd imagine easyJet held out on the route as long as they did, to maintain any contractual obligations they had with CPH.
If the CPH route at LTN continues with FR will be interesting to see how the pricing compares to STN. Maybe increase the prices, so STN is more attractive to use that route.
I suppose there is a slim chance they could operate side by side like the Dublin routes from both airports.