Dynasty Warriors 9 was announced this weekend by Koei Tecmo and Omega Force. The 15th anniversary of the Dynasty Warriors series looks to be a good one, with Dynasty Warriors 9 being considered a "rebirth" of the series.
Dynasty Warriors 9 will change from a mission-based system to an open world. There will be towns that you can visit and leave at will and all of China will be reproduced in the game (though at scale). Some places like Hulao Pass and Zhongyuan will be created in detail while others will be abridged for gameplay purposes.
Omega Force also stated that the traditional control method of Square for attack and Triangle for charge attack would be abandoned. It hasn't been stated yet as to how this change will affect gameplay, but it may allow for more dynamic controls.
The Dynasty Warriors 9 announcement came during a PlayStation broadcast, so PlayStation 4 is assuredly getting the title, but no other platforms have been confirmed. No announce date has been released for Dynasty Warriors 9, but more than likely Koei Tecmo will want to get it out in 2017 to celebrate the series' 15th anniversary.