Wasn’t the series originally supposed to be just 3 books when he first started it?

I made a similar mistake to this with the Game of Thrones series.

I was nearly done the second book when I went on a vacation, so I figured I’d bring the 3rd and 4th book with me. But before I left I decided there was no way I’d finish the 3rd book during my trip, so I took the 4th book out.

I was several chapters into the 3rd book until I finally realized that I had accidentally taken the 3rd book out of my traveling bag and had skipped ahead to the 4th book.

I had been wondering why so many key parts of the plot seemed to have happened off screen in between the two books, and when the plot points from the last book would start to be addressed before I realized the mistake.