It's not a matter of letting. The Japanese have every right to make their own works as they see fit. Can you imagine if the Avengers were made by the Japanese. People wouldn't stay still about that, would they. But the fact is that in America American companies hold the copyrights for those IPs and they have more to do with developing the American versions than the Japanese holders.
Anyway, I saw the trailer a while back and I like Miike and I like Blade of the Immortal so here's to hoping for a good match.