Automatically stopping at lights and signs would be a very significant update, not a sneak peak IMO.
Tesla can't release "beta" versions of stopping at lights. It's too big a liability.
That's my concern also. In the city, things happen more quickly than on the highway, even though you're moving more slowly. You have less time to take over from the car. But if the car just said "Red light ahead. Start braking now," that could be a "sneak peek." They could warn you that the car will not stop on its own and you still need to stop the car, but this could show how well the car would have done had it been making the decision to stop. And there would be data about how many false positives and false negatives the car made.
And if it can run on 2.0 and 2.5 and cars without EAP or FSD, it would also serve to nudge people into buying FSD by showing them how accurate it is.