My questions is how you are so confident that the game will be released in 5 months (4 months from now since your first estimate), considering that you haven't released anything other than the create a pirate. In this 5 month estimate, I also assume you mean a beta because you do need a reasonable testing time, for any game really. Assuming you do a very short beta (around a month to two months), I still think it's unreasonable that you will be able to create the game within the next 2-3 months.
If you still believe your own estimate, will the next update strictly be on port royal, or will you release more than that? Also when are you planning on releasing the next stage of progress. Although I am no developer, it just doesn't seem realistic that you will be able to complete every portion of the game within this time frame with the current rate.
Again, if you think your estimate is legitimate, I think me and many others would appreciate a rough timeline estimate (this may put too much pressure though) or at least a hint of what you have been working on or finished considering you describe the team to work very efficiently.
Don't let this put any pressure on you, as I am simply wondering why you are so optimistic about it, but my advice would be to not get ahead of yourselves because it would be much more relieving to know the game will come out in 10 months than think it will come out in less than 5.