Because of the massive success of 1989 as a pure pop album, Taylor does NOT need to prove anything anymore, so after RED which was experimental, we will see what EXPERIMENTAL really means

on TS6, I THINK.
Edit: For the lead single of TS6, the easiest choice will be a Max Martin collaboration, but it does not necessarily have to be MM, we got NEVER EVER from RED, we got SHAKE SHAKE SHAKE from 1989, the keywords are always the main factor. Edit3: And the keywords were/are always from Taylor Swift herself, not the other way around.
Edit2: The best way to experience different directions is working with different directions/collaborators, I hope to see more collaborators on TS6, I wrote about the logical and possibilities about this multiple times in this base.
Edit4: I agree with Retro, anything is possible on TS6, POP, ROCK, POP/ROCK, COUNTRY/POP......I even don't mind seeing some RAP......no JAZZ yet.