Just a thought on this - what's to stop Apple making an iWork app, where you could save the files? APp comes to those with iWork 09 perhaps
Apple seemingly wanting storage of files per app, rather than a central repoistory (beyond pictures, upcoming video, contacts etc)
I'd say it's potentially likely. That or a MobileMe app, to do the same thing - store any compatible attachments. If they could bring smart sensing of linking between apps, or working out which app to open for a fle type that would be great (user could give preferences).