ArcGIS Pro 3.0 is a breaking change release. If you share project files or datasets with older versions of ArcGIS Pro, use project packages and document packages (instead of not collaborating with others).
Installing ArcGIS Pro 3.0 requires .NET 6 Desktop Runtime x64. Install the latest available version to avoid delays when Pro 3.0 is released. (Download site)
There are new Excel driver requirements. Review and adhere to the information in the 3.0 documentation.
If you run ArcGIS Pro on concurrent use licenses, be sure to first update to ArcGIS License Manager 2022.0 before updating to ArcGIS Pro 3.0.