Yes, there is a plan. They've said that countless times before.
That said it wouldn't matter if the underlying technology even was in the redist since all your test accounts would have to have XBL Silver (for system link; Gold for LIVE multiplayer) and Creator's Club anyway. So if asking them to install XNA Game Studio is a big worry, getting them to all pay $99-$149 is probably going to be more of a deal breaker. Networking is currently the same boat as Xbox 360 development: it's currently a developer's playground. Eventually the restriction will be lifted, but for now that's the way things are.
Edit: After re-reading
this post on the XNA Team blog, PC to PC system link is totally free (too many stinking different scenarios :)). But the statement still remains that networking is a developer's area currently and not intended for XNA end-users at this time.