Some people might argue that this assumption might be a little far-fetched and the connectors are there just because they’re needed on the Model S. The thing is, the PCB is quite different on the Model S, so there’s no need to share this feature with the Model Y and let the second display port unused. According to Green, a similar situation appeared in the past, when the Model Y PCB had unused USB3 ports, but they got populated in later revisions.
A rear entertainment system makes a lot of sense in the Model 3 and Model Y, especially when the Full Self-Driving would become usable. The secondary screen would allow adjusting the cabin temperature and the rear seat heaters. It would also enhance the entertainment experience with movie streaming and even games. This would be useful to the rear passengers even while driving.
A second option would be for Tesla to introduce a digital instrument panel behind the steering wheel, like in the Model S/X case. This is unlikely, though, as we’ve seen Tesla moving away from this classic approach. Elon Musk has expressed confidence that Full Self-Driving would become available this year, so there’s no need to invest in a feature that will soon become obsolete.
Looks like model 3/Y is getting a second display soon?— green (@greentheonly) April 16, 2022
I just took a closer look at an AMD based model 3/y car thanks to some enterprising people
And there are two unpopulated connectors near display, one of them is marked "2nd display".
EPC has it populated - looks like s/x pic.twitter.com/99ESydFShV