I stand corrected. The website has not been updated, but their FaceBook page indicates that the computers are out, but the C64 is sold out at least in North America.

Yeah, all of these computers are manufactured in limited runs, and sometimes they go out of stock and all you can do is pre-order the next run and wait (this is currently the case for the ZX Spectrum Next for example).

However in the case of THEC64, you can still find it at certain international sellers, so you can have it now if you're willing to pay a premium for international shipping.