The story lines are pretty much easy and endless. TC, for the most part, makes really good movies and you have that huge built in audience.
My guess, Top Gun 3 will be the passing of the torch from Mav to Rooster and that young Val Kilmer dude.
Which will/could create a Fast and Furious or SAW or Mission Impossible, type of franchise. Where the name is still there but you can keep adding/subtracting the stars in the movies.