I think the true test will be when Confectioner revamp happens. If it's possible to get all the conf forms from the trainer in the same was that the dragon lairshaper trainer sells then it will mean that as classes get revamped or looked at perhaps the forms will get moved to the trainers. Keep in mind that lairshaper is the first class that has been designed for the new skill system and I suspect that the design of how their forms are delivered is part of that.
For the record I belive that the way that it's currently working for dragons is the correct way. I believe it makes far more sense to purchase the forms from a trainer and even though the price was elevated I didn't feel cheated by the npc like I do when I buy stuff from the Vielo.
Also keep in mind that players could offset the vielo by selling expert forms that drop rather than pawning them. If npc's sell the forms for reduced price then there's little point in having them drop from mobs.