Update 2/20/2020: ArcGIS 10.8 has been released.  View the post here.

Looks like ESRI pre-released ArcGIS 10.8.  Logging into my.esri.com shows what is available for download:

ArcGIS 10.8 Prerelease:

The ArcGIS Desktop and ArcGIS Engine 10.8 setup packages are designed to detect and upgrade an existing installation of the same ArcGIS product. The settings for the installation location, license manager (for concurrent use), or authorization information (for single use) are retained during the upgrade.

ArcGIS Enterprise 10.8 upgrades are not supported at 10.8 prerelease. To see the new capabilities of ArcGIS Enterprise 10.8 prerelease, it is required to do a new installation. Upgrades from previous versions to the 10.8 prerelease are not supported. Upgrades from the prerelease version to the final released version are not supported. The final release of 10.8 will support upgrades from previous software releases as usual.

The following products are not included with ArcGIS 10.8 prerelease and will be available with the final release of ArcGIS 10.8:

• ArcGIS Business Analyst Enterprise
• ArcGIS LocateXT for Server
• ArcGIS LocateXT for Desktop
• ArcGIS Monitor
• ArcGIS for INSPIRE
• ArcGIS Enterprise Cloud Builder for Amazon Web Services
• ArcGIS Enterprise Cloud Builder for Microsoft Azure

ArcGIS 10.8 Single Use Licenses:

If ArcGIS 10.8 will be installed on a machine that is different from where a previous ArcGIS 10.x product is currently installed, and you wish to use the existing ArcGIS 10.1–10.7.1 authorization number for ArcGIS 10.8, the earlier version of an ArcGIS 10.x product must first be deauthorized before authorizing ArcGIS 10.8.

ArcGIS 10.8 Concurrent Use Licenses:

• The copy protection mechanism for the prerelease version of ArcGIS Desktop 10.8 and ArcGIS Engine 10.8 concurrent use requires that ArcGIS License Manager 2019.1 be installed to support these products.
• Existing ArcGIS 10.1–10.7.1 authorization numbers will work with ArcGIS Desktop and ArcGIS Engine 10.8.
• Existing ArcGIS Enterprise 10.7–10.7.1 authorization numbers will not work with ArcGIS Enterprise 10.8. You must obtain a 10.8 authorization number which will also work with the final release of ArcGIS Enterprise 10.8.