Ryanair is to step forward and fill the gap left by Monarch with the new Malta routes and extra flights to:
Alicante
Faro
Lanzarote
Malaga
Palma de Mallorca
Tenerife
All of which are said to go on sale next week.
Interestingly it is reported they will have 36 routes in Summer 2015 (compared to 38 this summer), which I make including the new Malta route means three routes are being axed. I expect Cork to be one of them.
Source:
Ryanair steps in to fill Monarch routes at East Midlands Airport | Derby Telegraph