It's funny because today i was exactly thinking about how Kishimoto it's actually very smart planning Samurai 8, you see, every first SJ manga volume has 7 chapters, and when you look at the first 7 chapters of Samurai 8 as a whole, it's perfectly structured to be read as a first volume, you have 7 chapters where he introduce the main characters, work their personality, do all the exposition stuff about the world, powers and etc, and he finish chapter 7 (end of vol 1) with a spread page introducing a new villain with a super cool design to make the readers think "wow, now the story it's really starting, i'm hyped, gonna read vol 2!", and it's working with weekly readers!
Also, this is what makes me think that they will release vol 1 and 2 at the same time in October like Toriko, it would be a smart choice in my opinion.