Sorry; my lack of clarity Andrew. I think the commentators' emphasis was probably intended to be on the "general disruption caused" rather than any suggestion that Denon themselves may have been directly affected.
This comment also appears on the website of an Australian Denon dealer: "An end of an era ... no more 48 series and above Denon surround amplifiers... the nine channel 4311 will be the effective top of the range after the 4810 and AVPA1HD/POA are sold out... it has already been suggested that the tragic earthquake in Japan will prevent supply for some time of the higher end tier one brand product."
Edit: Apparently, the news of the 4312 being canned due to the turmoil in Japan came from Jeff Talmadge, Denon's Director of Product Development in the US, who participates on that particular forum. It'd be nice if WHF were able to confirm some of this with Denon UK: The rumours continue that the 4312 will eventually appear as a 4313 next year, but there never will be a replacement for the 48xx series or better.