In the Personal Data section, you have to list what classes you are taking/just completed and what are on your schedule/anticipated for your senior year.
In the Activities section, I think the instructions tell you to anticipate continued participation for the next year. I took this to mean that if you were on Varsity Football/Baseball/Whatever and you lettered as a junior, you're going to be on it again and letter unless you quit. Whereas, you wouldn't want to assume you are going to be elected President of the Student Body, because the outcome is much less certain.
You can update it later if you get elected to a certain position, finish Eagle Scout, etc.
