The Athletics agreement to play in the O.co Coliseum expired at the end of the 2013 season. The club and the Oakland-Alameda County Coliseum Commission have failed to reach an agreement on a new lease; the Athletics do not want to sign a lease that lasts longer than five years.
The team is also attempting to build a team with private financing in San Jose, but MLB is currently blocking the proposed stadium due to territorial rights. San Jose has an ongoing lawsuit against the league, which is currently stalled.
Matt Snyder of CBS Sports explains his frustration with MLB's lack of progress with the San Jose issue despite an apparent willingness to force the two teams to share a stadium:
What I personally find most aggravating here is that MLB could force the Giants to house the A's for a season (or more), but hasn't done anything of substance about the San Jose situation for over four and a half years. Nearly everyone wants the situation resolved and San Jose seems the most feasible solution, so the league needs to find a way to satisfy the Giants with some sort of settlement and just move on.
The Athletics still expect to work out a new lease agreement, and would like to stay in Oakland until the San Jose issue is settled, according to Purdy.