Maybe if Microsoft stops shipping 32-bit OSes. But if your app needs to run on 32-bit Windows, and your app isn't one that would benefit much from 64-bit, why bother releasing a 64-bit version? It's just one more build to keep track of, and one more source of bugs.
The WOW64 layer has a few caveats. For instance, filesystem virtualization means that users of your app may see different content in a "File > Open" dialog than they would in an Explorer window.
