Hi there Tracie, and welcome to the Disney Parks Moms Panel! I always love chatting with a fellow Floridian!
I was pretty sure I knew the answer to your question, but I called our pals in Guest Relations just to be sure. The Cast Member I spoke with confirmed my thinking, and also gave me some additional information to share with you.
First, a little housekeeping. Disney announced changes to the Passholder Program just a couple of weeks ago. For Florida residents, the Annual and Seasonal Passes have been replaced by the Disney Platinum Pass, Disney Platinum Plus Pass, Disney Gold Pass and Disney Silver Pass (the Disney Weekday Select, Epcot After 4 and Water Parks Passes are still available). The Disney Silver Pass is roughly equivalent to the former Florida Resident Seasonal Passes, with one big addition: the Silver Pass will now include parking at the Theme Parks! And if you decide to go Gold, you'll have parking and free photo downloads.
Now, to your upgrade question. The Cast Member who helped me said that you can indeed get the full credit for your Florida Resident 4-Day Ticket applied toward your new Annual Pass. She also told me that since you've used two of your allotted days, the anniversary date of your Annual Pass will actually be the date you first used that 4-Day Ticket. So, for example, if you used the first day of your ticket on October 1, then upgraded to the new Pass on November 1, the renewal date for your Annual Pass will be October 1.
Also, she mentioned that you'd need to visit a Guest Relations location at one of the Theme Parks or Disney Springs and complete your upgrade in person.
I hope this helps you enjoy all those Disney days to come, Tracie. Please stop by and see us again if you have any more questions.
Keep Disney Dreaming,
Kathy K.