First info about the Craft Cloud
Pixel & Tonic is finally ready to settle most of the open questions in March. Surprisingly, Craft Cloud is not supposed to be just a service for serverless craft projects but will become id.craftcms.com directly. So you should be able to manage your invoices, licenses, and plugin purchases through it as well.
Understandably, Pixel & Tonic would like to further centralize rather than a fragment. I would also like it if one login was enough, so I liked the idea of Craft ID and Cloud, which seems to extend now.
Craft Cloud replaces Craft ID in the first place, and that's why the user accounts remain free. Even those who are not interested in serverless projects need to be able to manage their invoices, purchases, etc.
However, those who want to use Craft Cloud for headless CMS projects will pay $20 per seat per month with no practical limits on content volume or API requests.
Pixel & Tonic plans to roll out in phases. License management, plugin management, invoice management, and self-hosted projects are scheduled to launch this fall. Serverless projects will come along with Craft 4 in early 2021.