Microsoft has already unveiled Continuum, a new feature in Windows 10 which handles the UI that gets displayed depending on what hardware you're using. Continuum quickly and conveniently switches you between a desktop environment and a touch-based environment, and according to Microsoft's Joe Belfiore, Continuum should be ready for testing by early next year.
Belfiore claims that the Windows 10 Continuum mode should be ready for Windows Insiders to begin testing by the end of this year, or at the latest beginning of the next. Right now, Microsoft is focusing entirely on the desktop side of things, which means their touch-based UI isn't as far along as the desktop features are.
Microsoft has already demonstrated what their vision for Continuum is via a video concept. Considering what was shown is a concept, the touch-based UI isn't exactly ready for primetime just yet, which explains why said feature is not available in the early Technical Preview builds.
It's good to know that Microsoft are working super hard to get new features out to Windows Insiders. The next major step for Windows 10 is the announcement of many consumer-orientated features, which is set to be unveiled in early 2015, perhaps alongside Continuum.