Good question, and it's something that should have been addressed in the announcement.
No, there won't be any new descriptions, names, or titles generated if your account has already posted them. This allows you to use the Bot periodically to rewrite descriptions for newly added products by other users without creating unnecessary duplication.
So, essentially, I can just enter the top-level list, and if there are any new products added by other admins, bot will rewrite descriptions only for these products, correct? Also, what happens to the canonical links for products that receive new descriptions?
1. Yes, that's correct.
2. If the new description doesn't receive enough approvals to replace the previous one, then your site will display the new description without canonical referrals. However, if another site has added you to their list of admins, the new description will also appear on their site, and it will reference your site as the original source of that product.