Today's Denver newspaper said that Walmart was going to first stop accepting the cards this month at their three stores in Thunder Bay, Ontario. Notice that they didn't stop first in Toronto or Vancouver. So, it sounds to me like they are sending Visa a message and may not expand the threat unless Visa refuses to back down.
We got our chip card three years ago to use at pay-at-the-pump gas stations in Canada, which always required a PIN. And, when Walmart started accepting chip cards in the U.S., they also required a PIN. But sometime in the past two years, Wlamart stopped requiring PINs and started requiring signatures. Don't know why they did that as I always preferred the PIN because no one can copy it off the back of the card like they can a signature.