I read from the devs that PVE Trials will be balanced for 12 players. Is there any possibility that if the population supports it consideration may be given further down the road for raids of say 24 players?

Who knows, maybe in another Adventure zone after Craglorn.

^^^^^ This, let the game get released, and the first adventure zone get into the game in the first update, I am sure they have some long range plans of some kind, I hope