That premise then begs the question - what is now being produced in Austin? Which Elon has stated is based on 4680's.My take is: the 4680 will be in Model Y's AFTER their production is ramped up enough to have satisfied the Semi at their full production levels. So this will take possibly a year out. Rationale is that for the mission (and profits) using 4680's in the semi is highest priority.
It is even possible the 4680's get rolled out for the CT even before M3SXYs
We cannot know until Tesla announces, or customers take deliveries of 'A' VINs.