Tsuburaya will be releasing the Ultraman Retsuden episodes in weekly installments on their Youtube channel.
Ultraman Ginga S: Showdown! The Ultra 10 Warriors is being aired on Shin Ultraman Retsuden in a three episode installment, featuring new scenes not seen on the home or theater releases. The three episodes will air as Shin Ultraman Retsuden episodes 139, 140, and 141. The episodes also feature new scenes with the Ultraman X cast.
Ultraman Ginga S: Showdown! The Ultra 10 Warriors was released on March 5th, 2015 and features Ultraman Ginga teaming up with various Ultra Warriors to battle a new enemy collecting various Ultraman from their home worlds.
Source: Tsuburaya’s Youtube channel