There's a lot of important questions and issues with this.
Does Apple really expect us to have iCloud as the main storage location for our photos? Will they provide proper tools so we can keep a complete, 100% local copy?
Imagine if someone could log into your Apple ID and delete your photos. Or if something goes wrong at Apple and your entire collection is destroyed? Being able to store your entire photo library on your own media is MANDATORY!
What about data plan usage? If you take hundreds of photos on a trip, it'll use a chunk of your data plan to upload that to the cloud. Then another chunk to download that to, say, your iPad, and again to your Mac next time you tether. Carrier bills are going to get run up quickly!
What about videos?
This is madness! We need more information. I work in IT; making sure data is safe is part of what I do for a living, and I have all kinds of doubts and concerns about this "iCloud Photos" thing.