Next Office for Windows 10 is only available via the store.
Microsoft has taken the other approach, if apps don't come to the store, the store comes to the apps.
So thanks to the outcome of Project Centennial, they are now merging the UWP and Win32 worlds into Windows containers and making the store Win32 aware as well.
I run Windows at home, but wouldn't if it went Store-only. For me, an open platform is the only thing Windows had going for it.