Complex sentence: The planned stadium, Cisco Field, was originally intended to be built in Fremont, California (a location that has since been abandoned), and there were talks about it remaining in Oakland, and current talks about building it in San Jose.
Split into simpler sentences: The planned stadium, Cisco Field, was originally intended to be built in Fremont, California (a location that has since been abandoned). There were talks about it remaining in Oakland and there are currently talks about building it in San Jose.