Earlier quoted context omitted.
what's stopping them is fsd has been promised on all these cars without those sensors. taking that away would likely mean a lawsuit
A promise isn't a contract, so whether it's actually guaranteed in the language in whatever agreements may be signed, will be the determining factor. And how the automative industry has functioned since its existence is risk-benefit-cost analysis, so if the cost of a future fallout is less than the short-term benefit then they tend to decide for the short-term benefit; most disgustingly in regards to known problems o…
Marketing is admissible in court as evidence of intended contract. Since marketing is generally easier to understand the legalese, if the court decides the marketing is misleading they will tend to punish you for that and accept the marketing as the shared understanding over whatever the letter of the contract is.
Note that I used a lot of wishey-washy words like tend... Each court case is different, and there is no real rule of what courts will do in any given situation. Consult a lawyer for legal advice about your specific situation.