The WiX Toolset team did their first v3.10 weekly release: v3.10.1124.0
Weekly releases are basically developer beta test builds and are not final releases. This release is interesting to me because it includes Visual Studio 2015 support. I've tested this build with VS2015 Preview and IsWiX 2.5.14324.3 and I find everything is working just fine. I can now relax knowing that I'm well ahead of the curve in supporting the next release of Visual Studio.