Dragon Eyrie after level 30
Level 30 is a far as it goes. I am only halfway there at level 15.
I suppose it is possible they would add more levels in the future but I doubt it. Pig breeding had a fixed number of levels and stayed there. Also it does not appear that dragon breeding is popular. Did you breed every possible combination? That is another goal besides level 30. I think there are 40 different dragons that can be bred using the various combos of parents.