I think the connection to LHR is far more important for connectivity than a connection to JFK would ever be. From LHR passengers can reach Europe, the East and West (even other UK destinations if they wish). JFK offers only US destinations, at a push Canada but there is a lot of back-tracking and clearing Customs and Immigration twice.
A US route would be a great feather in the cap, but links to BRU, FRA or ZRH would be much more useful.
dubh12000,
EK dont have a codeshare into Cork, but they do offer fares into Cork, mostly through on-line and high street travel agents (expedia, etc), they will connect over LHR, MAN, AMS, CDG and BHX, potentially GLA if the schedule and availibility works. They used to offer LGW as well, until EI stopped that route. Often via one airport one way and another on the return.