Via the IGN review of Dynasty Warriors 6 it is confirmed that, once again, Koei has left the Japanese Voice Actors off the American release of the game.
Let's review the timeline.
Chapter 1: I arrive at college, and see someone playing Dynasty Warriors 3 for the first time. I laugh at the horrible English voice actors, but get blown away by the inclusion of Japanese vocals. Addiction++.
Chapter 2: Dynasty Warriors 4 comes out, no Japanese voice actors. Bitter tears are wept, and the game goes unpurchased.
Chapter 3: In desperation, I buy Samurai Warriors for its Japanese voice actors. Sadly, the game has a "level up" system which punishes you for being strong. Gee, thanks. The game is sold back to Babbage's.
Chapter 4: After months of suspense as to whether Dynasty Warriors 5 will have the Japanese voice actors or not, the ill news arrives. Depressed but in dire need of a new "fix", I eventually cave in and buy the PS2 version. The next day it's announced that the Xbox version will have Japanese voice actors. D'OH.
Chapter 5: The Xbox 360 announces backwards compatibility! Great news, except the only Dynasty Warriors game on the list is #4. This is true even today, after numerous updates.
Chapter 6: Samurai Warriors 2 is released, sans Japanese voice actors. Hope fades.
Chapter 7: Dynasty Warriors: Gundam surprises me with Japanese voice actors. Perhaps the soon to be released Dynasty Warriors 6 will break the growing cycle of pain?
Chapter 8: Today, it sucks to be me.
I effectively give up. The arguments have been made time and time again for why Japanese voice actors are a perfectly simple option to make available. I'm through waiting on Koei to make a game that A) doesn't suck and B) has the Japanese voice actors.
Sadly, the options for "kill legions of enemies in a mindless fashion" are slim to none. Maybe it's because Koei crowds out all the competitors, or maybe it's because the competitors are all like N3.