Do you honestly think Ryanair would pay to use T2???? LOL!
T2 is being built with US Customs and immigration incorporated. It will primarily be used for longhaul carriers and im sure the few quality airlines serving DUB such as WX/BD/EY/IB/LH etc. It is due to open I believe in time for the summer schedule next year however I believe Aer Lingus will not be shifting their operation to T2 until October 2010!
Hope that helps!