What...just no. Starlight turning evil again would not make any sense and would be stupid. It would mean that all the development and progress she got the past seasons was for nothing
I'm pretty sure they are not going with that route for her.
What would Starlight be the princess of anyway? The princess of...friendship? We already have Twilight for that. Making Starlight a princess would be pointless and redundant.
Regarding Flurry Heart:
It's not like Cadence has a long life span like Celestia and Luna do. Somepony will have to take care of the Crystal Empire after Cadence dies. That somepony will be Flurry Heart.
I personally would like an episode about the batponies. I want to see where they live, what their lifes are like and how they came tot be as a sub-race.
What about you guys?