A surprise to be sure but a welcomed one. I can’t wait to see the senate in action again.
I would sacrifice my first born to get an ahsoka mention or better yet a quick glimpse.
- I personally don’t think he’s a ghost cause that goes against old and new canon that Sith’s can persists past death.
Bringing Palpatine back fully might derail things something though as not only would it question Anakins sacrifice to finally free the galaxy of this guy it would also pit Rey and her friends against an evil the galaxy has already overcome.
Therefore I'll stick with the explanation that he's just a sort of specter or, like in some works already seen, a prerecorded message.
Heck, maybe Palps has his own Sith Holocron that can talk.
Ideally Ahsoka, Sabine, Ezra and Thrawn. But since they're all more or less completely confined to TV-esque work I don't expect them to show up in actual movie canon.
I'm content that we're finally getting Lando back.
Only in the movies though as even in the old EU there were dozens of dead Sith spirits roaming around, be it Freedon Nadd, Exar Kun, Palpatine himself or Vitiate/Valkorion, who persisted in some way for more than 1300 years.
The skill of consciousness transfer was also a thing in the old EU where the dark side of the force allowed to place your own essence into a new body/host upon death und Palpatine actually did this twice.