Good news. Both the random nature of pre and the fact that a person who wanted to board an intl. flight and still use the abbreviated pre process could simply buy a fullly refundable domestic ticket to get himself through pre, call in and cancel for a refund and then board his intl. flight, make this a simple step forward.
On the inbound intll-domestic connection point, I presume that TSA will ultimately open pre lanes at some checkpoints exclusively used for such connections.