This is breaking news in this very moment.
Rumors that Canon will stop delivery of the 5D Mark III to retailers are going around, and getting louder by the minute. canonrumors broke the news and I also heard something about it from customers but did not yet have any confirmation by retailers. There is no official announcement so far. I don’t think that a firmware update could be the cause, since it could easily be applied as an update at any moment. The only plausible motivation for a recall would be a serious hardware problem.
But then this is just a rumor, nothing more. Hence, let’s wait for an official announcement.