The new movie would then be the third released, but the second chronologically

I interpreted your question to be looking for one word to refer to the movie in question. It doesn't have one word to describe it. It is a sequel to the first movie in chronological order (which, in the case of the Star Wars movies, was the fourth by production order) and a prequel to the first by production order or third (or, eventually, fourth) in chronological order of story line. Thus Attack of the Clones is a sequel to The Phantom Menace and a prequel to the original Luke Skywalker trilogy.