There is no limit to the number of photos you can upload to My Photo Stream over time, but iCloud limits the number of photos that can be uploaded within a given hour, day, or month to prevent unintended or excessive use.
There is no limit to the amount of photos you can upload to My Photo Stream over longer periods (such as several months or years). Photos uploaded to My Photo Stream or shared photo streams are not counted against your iCloud Storage.
Now we are getting somewhere. This gives me hope for the future. Link via @everydayscott.
Update: After looking at some other knowledge base articles with newer dates, I am clueless on what this article actually means. Move along.