By Mark Wakefield Washington Commanders head coach Ron Rivera has admitted that he does not know what the future holds for his position as the team’s head coach. The Commanders head into Week 18 of the NFL regular season with a 4-12 record and have already been eliminated from playoff contention. Washington faces NFC East divisional rivals the Dallas Cowboys on Sunday, in what could be Rivera’s final game in charge. According to ESPN, new Commanders owner Josh Harris is expected to begin making big decisions at the franchise in the coming weeks, which could involve a change of head coach. Alth…