Skymark Airlines purchased the naming rights for Skymark Stadium back on 2/2008. The contract that was signed at the time was a 3 year deal. According to Nikkan Sports, Skymark Airlines did not renew the contract before the extension deadline, meaning the name will now revert back to Kobe Sports Park Stadium (or Kobe Sogo Undo Koen Kyujo, 神戸総合運動公園野球場).
Kobe City will put the naming rights for the Stadium back up for sale, beginning in January. If the city is able to seal a deal, it will be the stadium's third such deal, most for a baseball stadium in Japan.
Kobe Sports Park Stadium was opened in March, 1988 and became known amongst fans as Green Stadium Kobe. The Orix Blue Waves moved into the park in 1991.
In 2003, Kobe Sports Park Stadium became the first Japanese baseball stadium to have their naming rights sold and purchased when Yahoo signed a 2-year deal worth 200M yen with Kobe City. And with that came the birth of Yahoo! BB Stadium.
Two years later, Skymark Airlines took over the naming rights by signing a 3-year deal worth 200M yen. The contract was extended under the same conditions after the 2007 season.
And even though it seems the Buffaloes will be pushing their connections to Osaka more next season, they still plan on renewing their contract with Kobe for the stadium in March 2011.
Incidentally, the contract on the naming rights for Kyocera Dome Osaka run out on 3/31/2011.