Well Garber himself said that if the Chargers leave then San Diego is a much more attractive market for MLS.
This is a really well written article, but two things sort of stick out to me.
1) The author doesn't talk about the funding mechanics for the proposed MLS/SDSU stadium.
2) The author seems to believe that teams leaving San Diego is a reflection of San Diego's sporting culture as opposed to a reflection of horrible horrible horrible ownership/management. The Padres haven't won in ages, but still are middle of the road when it comes to attendance. That might be a better indicator of what loyal fans might reproduce on the soccer side if treated well.