Blogging from the Microsoft Ignite conference in Chicago.
As you all know, the Skype4B server upgrade can be done as an in-place upgrade from Lync 2013. However, there are things to concider.
If the server is a Lync 2010 server, there is no way to do an in-place upgrade. Migration is the only way.
Lync 2013 supports the in-place upgrade as long as you can schedule downtime because the services are removed during the process. For enterprise pools you would have to stop the entire pool to upgrade, so users will have to be moved to secondary pool or downtime will occur(there is no option for co-excistense of Lync 2013 and Skype for Business in the same pool).
When it comes to the server OS, you would want to concider upgrading the server if you’re on WinSrv 2008 or 2008R2. The Skype4B server install will upgrade windows fabric to the latest version, but only on 2008R2.
Recommendation: Win2008 or 2008R2 should be upgraded to 2012R2.
Implication: The upgrade process to Skype4B will have to be done as a migration if your servers are on Win2008 or Win2008R2.