People who want to write apps for the Surface Neo and Windows 10X will have to wait a while longer. Microsoft is planning to offer a pre-release version of the relevant Windows developer kit "in the coming weeks" through its usual Insider previews, with a 10X-ready emulator and programming interfaces appearing on February 11th.

The months of lead time should result in a fair amount of apps for both the Duo and Neo when they're ready. Just how many is another question. That might depend on how quickly Microsoft releases more polished developer kits, not to mention overall interest -- you'll only see widespread support if app writers think the new Surfaces (and Windows 10X) hold a lot of potential.