I heard it would be years to hold Denver at United. And commuting from Den to any other UAL base can be bad. Isn't Sfo notorious for not being commutable due to weather?
All domiciles can be fluid. When I got hired in 2000, newhires could get Den. Based on the high number of vacancies, that will probably happen again some time in the future.
Having commuted to SFO on a two hop commute, I didn't find it 'not commutable'. It simply requires advance planning.