First and foremost, Terry Rossio is absolutely, positively and definitively, the screenwriter of Pirates 5. As I'm sure you know, the development and writing of screenplays are a constantly evolving creative process. The "we" in Mr. Bruckheimer's comments that you quoted was meant to be inclusive of Mr. Rossio."
Jerry Bruckheimer himself also took to his Twitter account just minutes ago to confirm the news.
"#PiratesoftheCaribbean screenwriter Terry Rossio doing his usual phenomenal work on P5"
We still don't know when production may start on Pirates of the Caribbean 5, although actor Kevin McNally told us exclusively that they are aiming for a summer 2012 production start.
Pirates of the Caribbean: Dead Men Tell No Tales comes to theaters July 7th, 2017 and stars Johnny Depp, Javier Bardem, Kaya Scodelario, Orlando Bloom, Brenton Thwaites, Martin Klebba, Geoffrey Rush, Kevin McNally. The film is directed by Joachim Rønning, Espen Sandberg.