Why not consider other platforms? How about the new Adobe Apollo? Or go one step forward, and make your app web-based by using Adobe Flex Builder? Currently we are writing a very large application using Flex Builder and its great! Development is very quick and easy (data, by the way, is coming from web-services we write in C#) My roots will always be C++ and Win32, but for new apps you have to consider other things than Microsoft's future support: Ease of development, speed of development, maintainability, etc.

I don't think the comparison to cross-platform C++ is a good-one. Think about Java programming. Java runs on a VM (Same as JavaScript, CSS and HTML run in the browser). Think you had to write Java code like: if System.OS.equals("Windows") // Do this... else if System.OS.equals("Unix") // Do exactly the same, just a little bit different... It doesn't make much sense, does it?