[UPDATE: Logan's director and Ryan Reynolds are now denying that this story is accurate.]
Twentieth Century Fox has been building and developing its mutant universe since Bryan Singer's X-Men debuted in 2000, and one consistent staple of the cinematic world has been Hugh Jackman's Wolverine. The character was well-received enough to warrant a solo film in 2009's X-Men Origins: Wolverine - which was largely criticized by fans, especially for the movie's portrayal of Deadpool, played by Ryan Reynolds. However, both Jackman's Wolverine and Reynolds' Deadpool have gone on to win back favor from fans, the former in The Wolverine as well as X-Men: Days of Future Past, and the latter in Tim Miller's Deadpool.
Jackman is reteaming with The Wolverine director James Mangold for a third - and supposedly final - installment in the character's spinoff series with 2017's Logan. Elsewhere in Fox's mutant universe, the studio is also developing Deadpool 2, which lost Miller as the director and has since tapped John Wick co-director David Leitch. Now, it appears the Merc with a Mouth will next be seen not in Deadpool 2, but in Logan.
The Wrap is reporting Reynolds recently shot a scene as Deadpool that will be included in Logan, likely as a post-credits teaser. The scene was directed by Leitch, but it's unclear what it will entail or whether Deadpool will even interact with Wolverine.
Logan takes place in a near-future point of the X-Men timeline, in the year 2024, whereas Deadpool was set in present day. So, the scene could either feature 2024 Wolverine and an older Deadpool, or be removed from the rest of Logan's timeline and be set closer to present day in order to pick up where Deadpool ended and potentially set the stage for its sequel.
Of course, no matter where in the timeline the scene takes place, fans will undoubtedly be excited to see two fan favorite characters appear in the same movie - and, perhaps, the same scene. Although both Wolverine and Deadpool appeared, and fought each other, in X-Men Origins: Wolverine, the adaptation of Wade Wilson was criticized for being too far removed from the comics - the Merc with a Mouth's lips were sewn shut, after all.
Still, despite the bad reception of their previous on-screen meeting, many have hoped to see the new iteration of Reynolds' Deadpool appear alongside Jackman's Wolverine - especially before the latter retires his signature claws and mutton chops. In fact, both actors have voiced their desire to see the characters appear together again, with Reynolds recently voicing a desire to see Deadpool and Wolverine team up in their own film, while Jackman said in 2014 that he hoped the two heroes could duke it out once again. Whether the Deadpool scene in Logan lives up to the expectations of fans remains to be seen, but nevertheless it is another reason to be excited for Jackman's (supposed) last film as Wolverine.
Source: The Wrap