When will the new Icloud app be available for the Mac Desktop?

What new iCloud app.

There is no App. iCloud Drive can be accessed on the Mac either directly through Finder, or through iCloud.com.

there is no need for an app on a Mac.

lvanatta wrote:

When will the new Icloud app be available for the Mac Desktop?

Yosemite is required if you want to synchronize data across multiple devices (using Icloud).

IS08 was the first part, Yosemite the second - in the change to ICLOUD use.