Do the in-browser storage services help this? Usually you need extra apps and some don't even have them. It would be nice if they didn't continue fragmenting. I suspect a large number of users don't know that it could even be mounted to their FS.
I don't see "fragmentation" (as you put it) going away, because each service has its own way of authenticating users and accessing the services, and each OS has its own API for mounting or synchronizing files.