The ThinScale Technology Platform, made of the ThinKiosk, Secure Remote Worker, VDA and IntlliPerfom software, is fully backwards compatible.
Meaning you don't have to have the exact the same version of Server and Console, to upgrade any of the client pieces, but most importantly you can simply run the msi on top of your existing environment will little to none downtime.
Functionalities related to newer version are disabled by default and if your client doesn't support them, you won't see any difference in the way the end-client interacts with the Console.
It is always recommended to have the most up-to-date version of any client and any Server and Console, due to constant changes we make in performances, database queries and bug fixes.
To have a better understanding, have a look at the Release Notes for both Console and Clients and see if the functionality and bug fixes apply to you.