Thoughts are that he's entering the Rumble and and will retire after losing to Undertaker at WM.
that's a lot better idea than the chatter about having Cena beat Styles for the Smackdown title, then face UT in a retirement vs title match at WM.
So for WM it's looking like:
Goldberg vs. Lesnar
Cena vs Styles with the opportunity for Cena to tie Flair's 16 'official' title reigns
Charlotte vs Bailey
I'd guess on the Raw side it will end up as Rollins vs Reigns for the world title (with Rollins winning the RR), and Jericho vs Owens for the US title, and probably Stohman vs Big Show.