Disclaimer: this is not legal advice and I do love my Model 3!
While I am an attorney, I'm not going to claim to be some kind of expert in this situation. In fact, I don't really practice much. That said, If I'm sitting in my office, and a guy walks in with the following story, backed up by written evidence, I'm taking the case. Easy money.
Customer went into local lawn mower shop. Salesperson said there is a new electric mower that, for now, can cut in a straight line, on its own, with you simply walking behind it. BUT...soon you will be able to just sit back, in an Adirondack chair, watching the mower mow your entire lawn without you doing anything. All you will need to do is upgrade the firmware in the mower...soon. You pay $5,000 for the mower, and another $1,000 for the Full Self Mowing capability that is coming soon. And the value of this will actually go up, because soon you will be able to mow other people's lawns without lifting a finger so everyone will want it.
A few years later, the customer still doesn't have the upgrade. Some people with this mower have a beta version that sort of works, and is fun to play with, but require so much supervision that it's just easier to mow the lawn the old fashioned way. It most certainly does not mow the lawn without countless interventions and because of that, relatively few people actually are allowed to download the firmware.
I'm rifling off a Chapter 93A Demand Letter, fully expecting to march right into small claims court 30 days later, filing a 93A consumer protection action. And I am fully expecting to win double and maybe triple damages, along with attorney's fees unless the lawn mower dealer makes a reasonable offer of settlement, which would basically be refunding the $1,000 at a minimum.
The only difference between this hypothetical and my Model 3 with FSD, is that the owner of Tesla is not the local shop owner, but the world's richest man. Unfortunately that's a really big difference.