The article is beyond wordy and hard to decipher but here my TL:DR. And please correct me if I miss understood something.

Currently Fusion 360 projects are stored in the cloud with “single storage”. The default save location in Fusion 360.

Autodesk is moving to “Fusion Hub” since they boast it’s better at collaboration and file management.

If you receive the email notifying you of Fusion Hub. You have approximately 30 days" to upgrade to Fusion Hub. Auto desk will allow you to “skip the process once”, but will force you to upgrade after 24 hours.

Once you start the process of upgrading the “Single Storage” will be remove immediately or available for 30 days for collaborative files. So if you are collaborating with others, ensure to tell them or they will loose access to the project.

Shared links to existing projects will be broken after the upgrade.

My favorite FAQ:

What if I don’t want to upgrade my data to Fusion Hub?

Since we are supporting only one location to store data, you will be required to upgrade to Fusion Hub.