The class-action part of this is moderately ridiculous; I'm not interested in seeing Rite Aid sued into offering the payment processing system I want to use, I'm just not going to shop there anymore.
The antitrust part, however, could theoretically have some standing, at least if the coalition was large enough. That is, if a very large percentage of the retail sector gets together, sits down, and says "We are going to offer one payment system and expressly prohibit the use of a competitor in order for others to support it", at some point it could get into anti-trust territory.
If retailers blocking ApplePay and Google Wallet is "a violation of antitrust laws," then so would retailers disallowing Discover or American Express!
While I'm not defending these lawyers, it's not directly equivalent. The merchant agreement for VISA does not prohibit the merchant from accepting Discover or cash. They have the option of not doing so, but it's not a requirement.
If it did, and further if VISA was owned by a coalition of very large retail outlets that made up a majority of retail sales in the US, then Discover might have an antitrust argument to make.
As with all antitrust things, it requires the monopoly or monopoly-scale collusion, and forced exclusivity rather than just market preference, for it to be a problem.
If no one sells a Linux PC because no one wants to buy one, that's not monopolistic behavior. If Microsoft requires PC manufacturers to use its software exclusively in order to sell Windows-equipped computers, and Microsoft is in a dominant market position, then it is.