The
official website has been updated, the official title revealed:
Fairy Tail the Movie: The Phoenix Priestess (劇場版「FAIRY TAIL 鳳凰の巫女」)
More info can be found here:
http://fairytail-movie.com/news.html
I couldn't get much of it, but apparently the main new character for this movie is named "Eclair".
And here's a new poster image: