I am alright with there being more dragons. Though, the eggs would no doubt be under heavy lock and key, or lost, or already hatched and doing as they please. From my readings, the Targaryen family kept the Dragon Eggs they possessed as the most precious of treasures. The eggs were usually placed in cribs, hatching next to the child they were placed next to. 

You are the GM, and therefore, God. Do as you please, and whatever you feel is best.