There will still be domestic UA flights; but I'd not be surprised to see routes like SFO-LAX relegated to the dustbin at some point. I'd expect UA has seen significant attrition to WN on that route alone, although UA IS still running full flights on the route. But they also cancel or consolidate a number of flights on a daily basis (such as the 9:30am sfo-lax this morning) which bumps everyone onto earlier/later flights.
The SFO-LAX market tends to be winner take all. If you provide high frequency and relatively load factors, you can get people where they're going right away whenever they arrive at the airport. Delays don't really matter because people just get on the next flight out, which is at most an hour from departure. If your schedule drops below once per 90 minutes in this market, you are toast. Frequency trumps everything else.
In the OAK-LAX market I fly, I have been astounded by Southwest's ability to sell just the right number of seats so that all, or nearly all, standbys are accommodated. And I haven't seen a VDB request in my last 800 flights. The west coast markets (and probably the east coast shuttle markets too) are different animals, for sure.