Likely - but here's the thing; this could very likely be permanent if they see no noticeable drop in their revenue / profits; or not enough to offset the money saved by refusing to accept Visa.
More to the point - a lot of banks offer both Visa & Mastercard, so for most folks it'd be just a case of swapping cards if they don't already have one (if they feel inconvenienced by the lack of Visa payments).