Probably a few years before it works reliably.
Right now, my car on v12.3 can find its way out of a rather tight spot in front of a gate, where I back it in every night to charge. It's all gravel, a low rock boundary on one side, block wall on the other and a couple of other cars directly forward in the way.
There's not much freedom of maneuver to get out from where it's tucked in. It has to curve sharp left to get clear (but without riding up on the rocks) then sharp right around the front of the parked cars, then head for one of the driveway street exits bounded by small boulders on both sides. Obviously there are no lines of any kind in this gravel, only the rough rock borders and the cactus-strewn yard.
Some days it's reluctant to move after I engage so I give it a little pedal, other days it starts and does the whole thing by itself, rather slowly. Noting that the view forward around the car is nowhere near as good as it would get from the wide-angle and low-mounted rear camera, plus the repeaters facing back on either side.
So, considering that it already handles this situation driving forward, I don't see why it couldn't do even better in reverse, and even better still in parking lots with some semblance of standard markings and/or islands. It's just not allowed to reverse right now, and possibly needs tens of thousands of hours of reverse- maneuvering video clips to teach the network.
There may be some things that will take years, and as I've always said, some things that really need as good camera angles looking forward as it now has backwards. But I see no reason that basic reversing maneuvers are beyond the scope of v12 anytime Tesla wants to devote the training resources.
(Does that mean I want to wager on Elon's hopeful timeline? Not a chance!
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