I hated when the EU tried to bring back Palpatine using a less stupid approach, and I hate this more by an order of magnitude since it's even dumber.Not much. There are two rumors. One claims Palpatine will just be a hologram while the other claims his soul is in a holocron. The first one can probably be debunked due to that said rumor also said that Rei will be Han's illegitimate child. So that just leaves the second rumor which was posted on either 4chan, Reddit or 8chan (can't remember which but I talked about it around page 480 I think so the answer might be somewhere there) and what I recall from it, it also mentioned Matt Smith as a Knight of Ren (and we know he's in the movie due to how poorly Disney has hidden it), that Snoke was actually Palpatine's host and that Matt Smith's character will become Palpatine's new host. With said rumor claiming that Snoke's death caused Palpatine's soul to return to his holocron container.
So I bet this is in the fucking script.