[Potential SPOILERS for Dead Men Tell No Tales.]
The Pirates of the Caribbean series has been extremely lucrative for Walt Disney Studios, having grossed $3.7 billion worldwide over the course of four installments to date. Disney is reviving the franchise in 2017 with Pirates of the Caribbean: Dead Men Tell No Tales, an addition to the franchise that once again features Johnny Depp playing the incorrigible pirate Jack Sparrow. Javier Bardem costars in Dead Men Tell No Tales as Captain Salazar, the undead pirate who has escaped from the Devil's Triangle (after years of being trapped there) and is out to kill every buccaneer left on the high seas - Captain Sparrow too.
It's been reported for a while now that Dead Men Tell No Tales will serve as something of a soft reboot for the Pirates of the Caribbean franchise. Orlando Bloom is confirmed to be reprising his original Pirates of the Caribbean trilogy role as Will Turner in Dead Men Tell No Tales and has said in the past that, as he understands it, the relationship between Will and his now-grown son will play a key role in the movie. It only makes sense, then, for Will's wife (re: the mother of his child) and his fellow Pirates of the Caribbean trilogy co-protagonist, Elizabeth Swan (Keira Knightley), to also show up in Dead Men Tell No Tales.
TooFab is reporting that Knightley will indeed be in Dead Men Tell No Tales, having secretly shot some material for the upcoming Pirates of the Caribbean film. Although Elizabeth's return in the film might seem like a no-brainer, TooFab is reporting that Knightley's character only appears in a "small cameo during the end credits". However, the scene supposedly sets up Elizabeth to play a more prominent role in Pirates of the Caribbean 6, should it happen.
Dead Men Tell No Tales costar Brenton Thwaites, whose character appears during the film's teaser trailer, previously let slip that the movie is about "a young man who wants to reconnect with his father, Davy Jones." The third Pirates of the Caribbean movie, At World's End, concludes with Will having taken up the mantle of Davy Jones and setting out to perform his task (guiding the souls of the dead to the afterlife), so it seems safe to assume that Thwaites was referring to Will and may even be playing Will's son himself. This also suggests that Will is still serving as Davy Jones by the time that Dead Men Tell No Tales picks up.
If Will is still Davy Jones for the majority of Dead Men Tell No Tales, then this would explain why Elizabeth isn't in the film until the end credits - as the two can only see each other once every ten years, before Will's son sets out to find his father. It sounds as though Will might be freed from his curse by the end of the film (or something dramatic along those lines), thus setting things up for Elizabeth to re-enter the picture and become an important player again, in the sixth Pirates of the Caribbean movie.
However things shake out, the larger implication here is that Dead Men Tell No Tales may set up future Pirates movies to be more focused around the Turners and less focused around Jack Sparrow. Captain Jack will no doubt continue to be part of the franchise for as long as it continues on, but seeing as the fourth Pirates installment (On Stranger Tides, which features neither Bloom nor Knightley) arguably showed why Jack shouldn't be the protagonist of this series - coupled with Depp's star-power having faded in recent years - this doesn't like a bad approach to take to reviving the franchise, either.