Yakuza is nothing like any Shenmue, nor any kind of successor. Often awesome itself but Shenmue (3) going to shit is irrelevant to anything Yakuza & vice versa. The narrative tones in all Yakuzas are completely different and so is the pacing, gameplay style and anything Shenmue was going for with its first grand entries. The one superficial similarity was the art style and visual quality occasionally and mostly in the Yakuza cut scenes looked somewhat similar back in the PS2 days. Maybe eventually there will be a slower paced immersive sim-esque Yakuza that does take on a story with beats similar to Shenmue on top of that but until then, it's apples to cucumbers. Both are fruit but unlike each other and for most they'd satisfy different cravings, though one can like both/one/neither. /2c
The trailer is good, it probably won't give us an ending either (maybe for the best, I bet the more it strays from following 1 & 2's plot seen here the worse it'll get).