This is a remake or sequel of the original King's Bounty that came out 17 years ago, which would become the precursor to popular fantasy turn-based strategy series like Heroes of Might and Magic, Disciples, and Age of Wonders. The original King's Bounty was released in 1990 (by the now-defunct New World Computing) and blends RPG adventure, real-time exploration with turn-based tactical combat.
You may also want to check out a different, extended gameplay trailer at GameTrailers.com, which has not been previously reported. (See Alternate Sources below.)
Correction: The gameplay trailer has been reported before, under "King's Bounty: The Legend - new screenshots and gameplay video" by TnS. Sorry for the mistake.