Difficult one to answer. Originally I had outline plans (include plot points, characters and some rough careers) for seven books - but as I have tweaked and added to the first two books (all that crazy creative process stuff), it has sort of thrown my plan a little off kilter (in a good way, I hasten to add). So, whereas I know where all this is headed (roughly), the journey may well be a little different to what I expected.
What is most difficult about gamebooks is that you are telling a story just from one person's viewpoint. Therefore, each book takes careful planning to ensure that the 'grander events' are being shown as well as progressing the other plot threads. It's actually quite tricky when you can't do the usual novel technique of jumping to another character/location. So that also means that some things have been changing (and will change) as I work through the books.
Nothing is set in stone, so yes I do have career ideas for the other books (based mainly on location/zones that will feature), but they'll probably change or get swapped around.