I imagine Office, VS etc are too big to "port" to Appstore model. Also people still use these applications in Windows 7 and so that would mean having two parallel versions of the same app and release features and support for both.
Office will be "store only" on the upcoming version for Windows 10, check Build presentations.
Isn't that just wrapped for the store in their AppV model not a true UWP app?
The distinction of what makes a "true UWP app" certainly gets blurrier with the "Centennial" desktop bridge, but it's still rather more "true UWP" than AppV is/was.
While it isn't a pure UWP app, it is a step into that direction and already a big difference from being a standard desktop app.