Maybe, but Netflix isn't some little 2-bit company, they're huge and definitely have the resources to build a new program. Now obviously, building a new desktop program to support a dying OS might not make that much sense, but if the customers demand it, Netflix can do it.
They don't need to build a desktop program for Windows 7 when they can show video in a browser.
The advantage of building a Universal app using Windows Runtime is that it will run on Windows 8/8.1/10, Xbox One and Windows Phone. That's more than half a billion users....
