I assume they're doing a bit of copying of the Marvel model here, what with stand-alone superhero films and the occasional coming together in a big event movie. Episodes VII, VIII and IX are the Avengers movies. These newly announced stand-alones are Iron Man, Thor, Captain America, etc.
Of course, the difference being that the big characters are established in the main episodes and then split off into mini-adventures, while in the Marvel universe the characters are established in mini-adventures and then brought together after the fact...