User blog comment:J Fan/Shanghai Disneyland’s Treasure Cove Revealed, Fifth Film Still Uncertain/@comment-2191897-20140401052806/@comment-1984959-20140401072717

It did take Terry Rossio and Ted Elliott almost 3 years (September 2008 - To Sometime before June 2010) to write Pirates 4's script if I remember correctly.
 * Wouldn't know exactly how many years, but it is possible they had been writing OST for over 3 years. Don't know what really happened, but can only assume from what was revealed online:


 * 1) According to Gore Verbinski, the Fountain of Youth was an idea considered for the concept of expanding the Pirates trilogy.
 * 2) Tim Powers has said that Disney optioned his book before P2 was released(courtesy of Rick Kieffel's interview on YouTube and Johnny Depp Reads forum).
 * 3) According to Jerry Bruckheimer, Ted and Terry found Powers' book during the filming of P2-P3 (courtesy of Steve 'Frosty' Weintraub of Collider)

So for all we know, they might have been writing around that time period. Almost the same thing with P5, except it was revealed that they've been working on a story as late as summer 2010(courtesy of Jim Hill Media quoting "Entertainment Tonight")

But looking away from the script and looking at the potential film itself. All we know, officially, it that it is in development. There are no more details as of yet, including when it will be released. Whether it will move forward, or not, and when it'll all these questions be answered is only in a matter of time.