Those have been out for a while. We'll never see it.
The MP7 has been around for a few years now and has become the darling of movies and video games, but is yet another HK uber-gun we'll never see in civilian guise here in the US. Interestingly, Fiocchi ammo in 4.6x30 is currently available and reasonably priced at $27.95/50.
Are any common platforms chambered in 4.6x30?