Oh I 100% believe this is a recipe for death and disaster anywhere but Japan. I also believe it won't be around in Japan in 12-24 months. Or if it is it will not be anywhere near as fun.
My guide tonight told us how many changes there have been to try to avoid major government intervention just in the 4 months he's worked there. For example, when it started the guides could get out of the carts to take pictures and stuff at red lights. Now they can't. Helmets are soon going to be required by the company as well. Don't get me wrong, I don't think that's a bad idea but it's less "MariCar" if you catch my meaning.
I am also amazed that they don't have four point harnesses and racing seats. Even back home in the US those are pretty standard on go karts these days and we only allow them on closed tracks. They actually don't have ANY restraint at present.
I'd also expect to see roll cages on them soon and the guide also mentioned that they were going to have to find a mechanical solution for the noise they make. To me that means they are most likely going to have to switch from a 2 stroke engine to a 4 stroke engine since you just can't make a 2-stroke very quite. That will mean more power which is good but also more expense. Additional costs are that they might need a stronger transmission, then a governor to limit the speed top speed since the 4 stroke engine will likely be more powerful and make speeding an actual possibility (which is isn't really today except on down hill straights).
Basically, they have a LOT of government scrutiny heading their way and most likely a LOT of overhead soon in cart upgrades to keep said government happy. If they can keep making a profit (assuming they currently do) through all that then they will probably exist years from now but much less fun. If they can't, well, I'd recommend trying this while you can.