Definately. Atlas was on here pitching his 'woolong device' a while back that was more or less a USB card. The problem with that though was he was requiring actual USB interaction (which is both impractical and insecure for run-of-the-mill POS). Anything USB is not going to work well for mainstream point-of-sale. In fact, one if the points of this thread is that the smartest thing to do to get bitcoin adopted worldwide is to utilize existing and already implemented technologies.
There seems to be a lot of nerdy initiatives (printing out flyers, hacking credit card processors, etc) which shows heart in our little community, but it's basically the equivalent of trying to sell girl scout cookies to pay for a heart transplant.
The future of bitcoin merchant solutions is going to be a paypal-type service, smartphones and QR codes, and easily
implementable payment processing solutions for existing POS.
I'm not a mobile developer personally and the paypal-type site is for a different thread. I'm focused on implementing a datacenter payment processing handler that can be plugged in to existing POS machines just as simply as adding AmEX or a gift card to your accepted payments is (it's all handled server-side, no POS hacking required).
The only yet troubling issue is a bit of a touchy one:
Who should be responsible for the security of a customer's wallet?
Excluding near-field, a debit solution would be to hold the wallet on a card and have an actual transaction take place, but this would complicate things immensely (especially for near-field) and require merchants have a card-writer/reader (unlikely to happen).
An account based service however is quite practical and would allow for instant debit without worry of double-spend attacks. In this scenario, the e-wallet would be the payment processor (what MtGox is planning in Japan).
Wallet on card is acceptable, but I think the debit type bitcoin transactions is where we are all heading..
Being able to use a home wallet or just as easy to have a bitcoin bank account service is the way to go
Everything is set up for that already..
So yes, we should be piggy-backing the current infrastructure, like your saying.
I want something slick like those cards.. just a tap, maybe a swipe of the fingerprint, Bam.. transaction completed.
I also think those cards could run a client of sorts. Someone needs to take a serious look at them.