At some point USS cars will definitely get this park assist. The only question is whether that will incorporate USS data or whether those sensors will be disregarded for parking purposes from that point.I kind of doubt the USS cars will ever get the vision-only park assist. Tesla doesn't have any incentive to put resources into developing software marrying the USS and vision-only system. I could be wrong, but I don't think the USS cars can simply use the vision-only software for the park assist stuff because there would be competing signals that would need some sort of logic to sort out.
The transition is inevitable. USS are a very crude tool (much as everyone seems attached to them) and are no good for supporting the level of automation that Tesla need for their self driving features.