LibreOffice will probably be available offline for a very long time. Traditional ofline FOSS versions have been avaible for a handful of operating systems for years.
That said, I don't understand why we need a "web app" version, since many LibreOffice users (including myself) are likely suspicious of program that run in "the cloud". As Microsoft has proven time and again, using cloud apps allows whoever is hosting those apps a greater amount of power than traditional apps. That means more control, DRM that's much harder to crack, and complete control over the users'Forum (lack of) privacy.
On a brighter note, I've been hoping for an Android port of LibreOffice for some time. Finally, a portable office app that respects the freedom of the users.