Express News released an article about an hour ago saying the city is now seriously considering Hemisfair for a new arena, and that a city official discouraged the Missions' owners from pursing it for a new stadium because they were looking at it. The article mentions Lot A (south) for Alamodome as a potential site which would be really interesting, but there would need to be a serious conversation about flattening I-37 in that spot...or build tunnels.
The Spurs, Missions and the Roadrunners all within eyesight of each other is the future.