I'm sure they would want to carry freight; BKK is a very useful freight hub for Asia (although HKG would have been better), so basically, they're down to a choice of 777s or A340s and as you say, the latter - thanks to the DAA's lack of foresight (not to mention obstinate refusal to even consider a runway extension) - is out. Pity, because although EI probably prefers the 777 as an aircraft, I'm sure it would prefer to take A340s, given their commonality with the A320/330 fleets; much easier to integrate? (Mind you, perhaps Boeing might be able to supply a few 777s, if EI chooses the '87?)
Even if the DAA were to consider an extension, how long would it take - their argument would probably be that between the planning and all the various procedures, it wouldn't be possible much before the parallel runway is open, so let's just wait for 2012, when the new runway is open. So, five years before EI (let alone, DUB itself) can gain nonstop access to the far east. I sincerely hope someone raises the issue of DUB Airport in the upcoming election.