Unfortunately Martin has not completed the book series so I couldn't say what the final end will be for the dragons. But no they haven't run away. The TV series is moving into a point where Daenerys discovers more and more that having the living functional equivalent of WMD is not exactly a cakewalk. The TV series is also moving into a point where Daenerys' storyline in the books anyway got bogged down. I mean really bogged down.

However Martin has told the showrunners what he expects the ending to be. The TV show has already pulled stuff ahead from future books in the series and unpublished books so I expect that we will see more than few dragon scenes in the second half of this season. My guess is the CGI is expensive so they only use it when 100% necessary. Per Martin the dragons still have a lot of growing to do. This is Martin's conception of how large a full grown dragon is.