Apple and Amazon are the two major companies that could really shake up the "mobile payments" landscape. To some degree Apple is on deck to do that with its mobile wallet Passbook. However consumers remain to be educated about Passbook and its capabilities.
In addition, we're eventually likely to see iTunes stored credit cards become available to Passbook -- though the current iPhone is incompatible with NFC. Execution at the POS thus would be an issue unless Apple uses different materials in its future handsets.
Amazon is another "sleeping giant" in the realm of mobile payments. Indeed, from an "m-commerce" standpoint, Amazon is already in mobile payments with its existing "Checkout by Amazon" platform. However TechCrunch reported a rumor that Amazon was developing a Square competitor (SMB dongle). I wouldn't be surprised if it happened -- and relatively soon.
Amazon already has a developed payments infrastructure that supports e-commerce (online and in mobile) as well as a peer-to-peer PayPal rival. In addition Amazon may be second only to Apple in terms of the number of consumer credit cards it has on file.
While Apple claims 400 million consumer credit cards on file, Amazon has something above 200 million. The company could almost flip a switch (notwithstanding the POS issues) and become a major player in "mobile payments." It could also quickly enter the segment with the introduction of a Square-like dongle and/or the acquisition of another mobile payments provider (e.g., Braintree, Boku).
We should expect news along these lines from Amazon in the next six months. I would be very surprised if the company sat on the sidelines very much longer.