No other specific details, design or mechanical, have been provided, with one exception: the new Mirai will indeed be rear-wheel-drive. Because of its expected platform, the only alternative would have been all-wheel-drive.
In general, the images we have show a concept vehicle that is, at the very least, 95 percent production ready inside and out. The leap from the current Mirai to its successor is significant. Toyota could have easily sold this as a Lexus but opted to keep it as a member of its mainstream brand. Its coupe-like exterior styling looks fantastic with its lower, longer, and wider dimensions and 20-inch wheels. The interior includes a Toyota Premium Multimedia system with a 12.3-inch high-resolution touchscreen with navigation and a 14-speaker JBL sound system.