I'm confused now. I didn't think this announcement was to allow apks install on Windows 10. Simple ask: Will you be able to download the Amazon App Store apk from the handset's browser, install, and run the app?
http://arstechnica.com/information-technology/2015/04/29/mic...
"Unlike Islandwood, which will require developers themselves to recompile their software to bring it to Windows, Astoria will in principle work with any old APK, without requiring the developer to do anything but publish the app in the store—as long as the APK sticks to the APIs that Astoria will provide."