Have been doing migration of ADFS from W2008R2 to W2012R2 in recent days. There are couple of ways to do it but I like migration most because it can be done without any user impact.

Migration process at high level:

  1. Export, record, and backup the following configuration data in your existing AD FS farm.
  2. Create a Windows Server 2012 R2 federation server farm and install additional servers to farm.
  3. Import the original configuration data into this new Windows Server 2012 R2 AD FS farm.
  4. Configure and customize the AD FS sign-in pages after migration.
  5. Test new ADFS farm functionality from a PC connected to the domain, edit the hosts file and add the IP address of the AD FS 3.0 server that points to the new AD FS 3.0 Farm
  6. Test SSO to relaying party applications
  7. Do production cutover By updating external and internal DNS Records to point new farm

Exellent guidance can be found from here:

Kelsey Epps – Office365 MVP bloghttp://office365support.ca/migrating-ad-fs-2-0-to-ad-fs-3-0-for-office365-single-sign-on-2/

Migrate to W2012 R2https://technet.microsoft.com/en-us/library/dn486815.aspx

Migrate to W2012https://technet.microsoft.com/en-us/library/jj648428.aspx