Microsoft announced version 3.5 of Linux Integration Services for Hyper-V. An ISO-image is available for download at Mirosoft's site.
In one of my earlier articles I was wondering if it really matters when Hyper-V indicates the Linux guest status as degraded and tells that an upgrade is required. This version does not change that. Looks like they just added some (weird) new features and improved set of virtulization features for Windows Server 2012 R2, but didn't touch the network code. However, there is a promise of TRIM-support for 2012 R2.
So, the bottom line is: not worth upgrading.