see ryanair have applied to operate a kerry-dublin service. I can not believe there are serious with such a route, since snn-dub was cancelled after only 3 months.
Kerry is a good bit further from Dublin than Shannon is. The problem with SNN-DUB was that Dublin was to close to Limerick. Trains from Limerick to Dublin take as little as 2 hours 20 minutes. By the time you'd get to Shannon, probably be there an hour before the flight, take the 45 minute flight and then get from Dublin airport to the city centre (at least 45 minutes during the peek periods the flights operated at), it clearly made little sense to fly. Tralee-Dublin on the train takes 4 hours, nearly twice as long. KIR-DUB would undoubtedly be far more popular than SNN-DUB.
Also Ryanair operate Cork-Dublin flights quite successfully. Admittedly it has taken a while for the service to become established against the popular Aer Arann service. However they now seem to be doing quite well with their 5 times daily service.