Is there any way to write a WinRt (Metro) app that will also work on Windows 7 and Vista?

Question

We can’t just leave our customers that are not able to upgrade to windows 8 for a long time in the larch. However there is demand for a “tablet”/”touch” version of our app.

So how can we support both touch with Metro on Windows 8 and our current customers from a single code base?

When WPF come out, after a lot of “Pushing” Microsoft saw since and make it work on Windows XP – has anything like this been talked about for WinRT.

(I am not expecting any solution to work on XP, as XP support is being wound down.)

See Also: Can the ARM version of Windows 8 only run Metro (WinRt) style apps?