1.) Too late. No way they can make a dungeon by early may at this point.
2.) This will bump the number of trials up to a grand total of 7 after 4 years. Do not begrudge trial teams a new trial.
3.) This is not their only chance to use summerset assets for a dungeon. If they do 4 more dungeons this next cycle (again) then there is a great chance they use those assets. I too love new dungeons. But I understand that this chapter is kicking off a year long cycle where the new DLC content will be themed appropriately, and that cycle will include the dungeons.