If it's anything like Android, it will be open enough (well, completely open, actually) that you can hack it to make it do what you want. You could hack it to work with Yahoo or Microsoft, or DedaSys, for that matter.
Well, OK, I have an old Mac SE/30 at home. It's a fine machine for basic word processing etc. I'm running Word 5.1 on it, how old is that? Yet despite it being closed source, Microsoft, utterly unsupported, yadda yadda, it works fine. In 20 years, will I be able to have my own completely independent Google Docs running on a Unix that doesn't exist yet, in a datacentre operated by a company that doesn't exist yet, and have all my old docs still there?
Basically, I don't think this has been very thought through.
Basically, I don't think this has been very thought through.