The Aer Rianta company had plans many years ago to extend the existing runway by I think either 300 or 400 Mts at the terminal end the details were on their summer timetable I can't remember what year it was.
This project got shelved when talk of the new runway started,I'm not sure how it might fit in now with T2 and a proposed Pier F also in the current plans.
The Fingal master plan had protection for extending the runway at both ends,there is close to 980 meters between the end of the runway and the roadway at the opposite end to the terminal so it might make more sense to look at that end if they do decide to extend the present runway.