Marvelous Games has confirmed that Fate/EXTELLA: The Umbral Star will be available to buy in North America from January 17th. In the UK the release date doesn’t seem to have been nailed down completely with Amazon listing it for January 10th, while GAME currently has it for January 13th. The game itself will feature three different perspectives, and will have characters from other Fate titles make appearances.
Fate/EXTELLA: The Umbral Star will be available for both PS4 and Vita.
Source: Press Release