It will not be set in the wish realm, I am certain of that.
Some things that I suspect may or may not happen:
– Magic will be “destroyed” OR Magic will be unleashed across our world and not limited to Storybrooke. They could go either route with this, but I do wonder if they may take a break from some of the more fantastical elements to try and ground the show again.
– The wall between lands will close off in order to protect them from the destruction of the new curse.
– Storybrooke will be destroyed / the show will be set elsewhere next season. Again, this could be good for the show because it features very few “real world” locations these days and relies heavily on CGI. CGI costs money and they have said that they want to cut costs (although losing cast also helps with this).
– Emma will not die
– Someone will be “banished” in the same way that the Black Fairy was. I could totally see them using this as a way to get rid of a character but have them return at some point.
– The new cast members are non-magical and have not been exposed to magic before. This could be used as a way to reintroduce the concept of magic in a grounded way.
– Zelena will die OR not. They have either beefed up her role in recent episodes because a) they are going to kill her off and want it to have more of an impact or b) because she will be featured more heavily moving forward (presumably alongside Regina)?
– If people stop believing in magic, does it still exist? The word for the finale is apparently “belief” and it would be interesting for them to play on the fact that a lot of the fans don’t believe in the show anymore.