Even Dublin struggles with the Ryanair effect. The only real alternative services offered beyond Ryanair and Aer Lingus are either major carriers along the lines of Lufthansa and Air France or routes that are too long to interest them - Long Haul, Istanbul etc.
I certainly can't see the latter showing interest in Cork and the former is very unlikely.
If any other airline were to come in, they'd probably have to do it in a big way, by basing an aircraft and offering several routes. A single route is too easy to pick off.
I always felt that was a mistake Easyjet made. If they'd offered Edinburgh, Glasgow, Barcelona, Milan etc instead of just Gatwick, Ryanair might have had more reticence about the amount of cash that would have had to be burned to counter them.