The popular blue Planeswalker Jace Beleren is the primary focus of the promotional tease, which promises more details "this fall". While not explicitly featured in the image, the vampire Planeswalker Sorin is generally associated with the Innistrad storyline, and could well be featured in the expansion.
The copy reads:
"Darkness is rising on the plane of Innistrad and its inhabitants need protecting from evil! The new Magic: The Gathering Arena of the Planeswalkers Shadows Over Innistrad tactical board game introduces new twisted terrain, powerful planeswalkers and deadly battlefield scenarios."
The first expansion set, The Battle for Zendikar Board Game Expansion Pack released in January, and featured Ob Nixilis and Kiora (see "First Expansion for 'M:TG' Board Game Announced").