Dragon's flying around and attacking would be cool.
They already exist – there are dragon events in a variety of areas that repeat every few hours. And some of them fly every once in a while ^^
More dynamic events like this will probably appear whenever we get a content patch that includes the dragons as a focal point.
For example, the next time our adventurers are given the task of facing jormag, or another elder dragon, it’s very possible in the same patch we will likely receive dragon related events and encounters in the related areas.