I am happy to announce that the latest and greatest Q2 2015 versions of UI for ASP.NET AJAX and UI for ASP.NET MVC work as expected under .NET 4.6 and fully support the new version of Visual Studio 2015.
Let me show how quickly you can create new MVC5 and Web Forms 4.6 projects with VS 2015 using the predefined Telerik VSX templates:
Before We Get Started
We should ensure that we have installed Telerik ASP.NET AJAX and MVC VSExtensions on our development machines. They will allow us to not only download the latest version of the controls, but also to obtain the predefined templates that will help us create new Telerik based projects. The fastest way is to launch the "VS Extensions and Updates" dialog (see Image 1) from the Tools menu, search for "Telerik" and install the AJAX and MVC extensions.
Figure 1: Install the Telerik ASP.NET AJAX and MVC eVSExtensions
Create a New Telerik MVC 5 Project under .NET 4.6
Once we got the extensions installed, we can go to File -> New -> Project... in Visual Studio 2015 and select Telerik ASP.NET MVC Application under the Web node as shown in Figure 2.
Figure 2: Select Telerik ASP.NET MVC Application and click OK to launch the Project Configuration dialog.
Click OK to launch the Project Configuration dialog. For our example we'll choose the Grid and Menu template (see Figure 3).
Figure 3: The Project Configuration wizard allows you to specify useful settings such as the project type, targeted MVC version, the View engine, the controls theme and many more.
Once we are ready with the configurations click Next and Finish to complete the project creation. 
Figure 4: The Solution Explorer is populated with the Project Template controllers, views and other resources.
To launch the app in your browser hit F5 or start the Index.cshtml in the browser using Ctrl+Shift+W.
You can see the result in Figure 5:
Figure 5: The responsive Grid and Menu ASP.NET MVC 5 app in action.
Create a New Telerik Web Forms Project under .NET 4.6
To create a new Web Forms projects for .NET 4.6, open the New Project menu of Visual Studio 2015: File -> New -> Project...
Go to Templates -> Visual C# (or Visual Basic) -> Web and choose Telerik Web Forms Application and click the OK button to launch the Telerik Configuration wizard:
Figure 6:Select Telerik Web Forms Application and click OK to launch the Project Configuration dialog.
Click "OK" to start the Project Configuration Wizard:
Figure 7: The Telerik Web Forms Project Configuration wizard allows you to specify useful settings such as the project type, the controls' skin and others.
For the purposed of this VS2015 test, we'll choose the Responsive Web Application template type and the Bootstrap skin. To complete the configuration, subsequently hit Next and Finish. This will load the chosen template files and folders in the studio:
Figure 8: VS2015 populated with Responsive Web Design project.
To preview the template project in the browser, select the Default.aspx page and either press Ctrl+Shift+W or F5. The app will be populated and you can test its responsive behavior as shown in the animation below:
Figure 9: The responsive ASP.NET Web Forms app for .NET 4.6 in action.
Conclusion
As beforehand examples demonstrated, there isn't anything fundamentally new in the new minor versions of .NET 4.6, Web Forms 4.6 and MVC 5. The Telerik Web controls are fully operational and work flawlessly under the new environment.
If you are planning new development under the new .NET 5 and ASP.NET 6 environment, you might find interesting the following blog post: Telerik Web UI products now support VS 2015 RTM.
