Guess who’s back!
Since they’re apparently going to visit the wreck of the DS2, I’m guessing Palpatine might appear as either a Force Ghost, or more likely, as some kind of Force Vision. Might be similar to the Thrawn trilogy where the death of the Emperor left behind an imprint in the Force.
Or Lucasfilm could just be messing with us in the trailer. Wouldn’t technically be the first time.