Kentico wrote an article about this in April:
What about ASP.NET 4.6?
ASP.NET 5 is not only version which is in progress. Microsoft is preparing another new version called ASP.NET 4.6 (currently in preview along with ASP.NET 5). This version is an evolution of the current framework and will probably not contain too many ground-breaking changes. We have already tested this version using Kentico and there are only small issues which can be resolved quite easily. My hope is that ASP.NET 4.6 will be supported as part of with Kentico 9, but this will depend mainly on the release that of ASP.NET 4.6.
Haven't seen any other comments about it, so pretty sure it won't be fully compatible with version 8.2. But just to be sure I'd contact Kentico Support (email@example.com).