Yeah.. what PEN said..
Why would Aion need to release a trial?
You do realise it had 400k prepurchasers, has stayed in the top 4 on xfire every day since it's been out, and actually had troubles at launch because TOO MANY people were playing.
There is no chance in hell there will be a trial for a while, and I don't see anything wrong with that.
Maybe if somehow they lose 90% of their subscribers in the first 2 months they'll realise something is up, but right now it's been the most successful launch since WoW.