In one of the X-Men stories they do a time travel arc where they run into a rather bizarrely behaving Deadpool. He sees Domino and says something like "I know you. We used to work together."But it wasn't a funny Deadpool. Insane in a different kind of way. Maybe the closest Deadpool can get to Alzheimer's, but still alive due to his healing factor. So it isn't impossible that we could see Deadpool, which would be great given his joking about Hugh Jackman. But I'm not sure Ryan Reynolds or, well, anyone, ready for somber Deadpool.

I'm assuming Liev Schreiber will be back as Sabretooth. Due to Sabretooth referring Logan as his brother in the leaked script info. Also Sabretooth's role is meant to be a twist in the film. Which is probably why we haven't heard anything about Sabretooth in this film yet. If it's a different actor playing Sabretooth, then the twist won't make much of an impact. It is revealed that he was working for Mister Sinister on the extinction of the mutant race this whole time.
Again, if the leaked script is true anyway. But then again, the leaked info for Ghostbusters was 100% accurate as well.

thanks a lot for the info! that just blew my mind, any idea who's playing Sabretooth? i would definitely stay away from cgi-ed Sabretooth, hopefully everyone feels the same. Has it been confirmed that Sabretooth will make his appearance with his arms crossed over his chest?

If the leaked script info is true, then
Sabretooth will indeed appear in the film. Also Iceman might appear as well.