No. Brent Simmons (author of NetNewsWire) wrote a post precisely about that 1.5 years ago

http://inessential.com/2011/10/25/why_just_store_the_app_dat...

If every app did automatic OPML import/export, sure. That would keep your list of subscriptions in sync.

I was thinking more of propagating the read state of the feeds.

Maybe just a script that can run occasionally and dump the new items as a single HTML page (plus another file with state info) into Dropbox.