I suspect that both cars (shaft/belt) will be available in the U.S. at around the same time. How each one will be presented to the market lies the true story of the two cars.
Like someone has already posted, the parts for the shaft car is almost all completely tooled due to iits offroad sibling. If you look at the arms on both cars, they look very finished. Therefore, parts are available for them to package a shaft car. Given that the parts are injection molded, it is obvious that this will be the car marketed to the masses. Kind of what the TL01 or the TT01 is for Tamiya except better.
However, if you look at the belt car, everything short of the arms and hubs, which are carry overs from the other car, is a custom machined part. In fact the front and rear bulkheads look very Atlas 'ish. (4 bolt shock mount) So similar to Tamiya, Kyosho may present this as a limited edition "go for broke" Team Car, like the 414s, 415s and so one. This will be the car for the competitive sportsman who needs a top level car to compete with.
So its only a matter of time when production, packaging and shipping will be done before we see these products on our shores. Average time for product to cross shores is about 6-8 weeks including customs. If we're all looking to see the product on the shelves in the next two months, we should all hope that product is already on the water by now.