So, yes or no, 104 weeks after a full power down and earning no SP rewards, will my SP balance be 0?
Even if you get no rewards, the balance is still going upwards due to the programmed growth. So the answer is no.
If you have 1000SP to withdraw, and you get no curation or author rewards, you'll get the 1000 out in 104 parts, but when you have finally pulled out the 1000, there will be more in your account from the "interest" of the initial 1000.