I would like to offer another perspective...
IMO the first trilogy sets up a redemption arc for Captain Jack Sparrow. Davy Jones Locker in particular creates a reality that represents Jack's "hell" by not being able to escape himself (ship on land + stuck with unhelpful multiple Jacks = not being honest with himself/escapist character), contemplates if he should or shouldn't stab the heart (Will tries to explain being the Captain of the Flying Dutchman requires doing a specific job), and by the end of the film, it's clear Jack put Will in a precarious circumstance and has ruined the immediate future of Will and Elizabeth, as Will can only step on land every ten years. (POTC is full of torn love stories.).
So when POTC:OST was announced I had read a couple of things. 1. It was meant to be relaunch. 2. On Stranger Tides is the name of a novel by Tim Powers and that Disney almost optioned the novel at the time of the first film and passed (but I read it several times and there are many ideas from it that are sprinkled across the series).
The relaunch made sense to me because in theory, if I was right about a redemption arc, then the logical course would be to dive further into Jack's past and then use those things to eventually catch up to Will and Elizabeth to "set things right".
OST featured Angelica, Jack's own love-torn revenge story (which seems unfinished), from a women who feels she has been done wrong by Jack. (In truth, we don't know if she bares any responsibility on her own fate) But more over, Philip and Syrena provide a "solution" to the Will and Elizabeth dilemma, as a clergy boy falling in love with a mermaid is quite "ideal" to become the Captain of the Flying Dutchman, as the job is to "ferry the souls of the dead" to the other side...
However, DMTNT has now found a work-around, but it still is diving more into Jack's past with the compass and the Trident (the trident first appears in young Jack Sparrow novels for kids). Jack's Uncle could also feed into unused plots from OST novel, and of course the final scene post credits, basically "resets" many curses and thus it's possible they have to revisit a Davy Jones dilemma again and find a solution that is not Will--thus Philip could still come into play here.
And at the end of the day, we see that Kiera Knightley's comments in particular are false, whether it's that she didn't want to tarnish her career, she knew there was a possibility, but wanted to discourage the audience to surprise them, or she was also paid the right price. So I think one way or another there was a plan to only do a film or two without Bloom and/or Knightley.