I just asked my SA (in KC) yesterday about this for my delivery (scheduled on 8/30, F536, BTW I moved from KS to WA this year). I hope this helps.
This is his response:
There is a chance that your Model Y will not have the mobile connector with it but we are sending out promo codes for customers who ordered before the cut-off to order a mobile connector bundle free of charge. You can also ask the team in Seattle if they have any mobile connector bundles in stock at your delivery.
I plan to simply install 240V NEMA14-50 socket in the garage no matter what while waiting for delivery. This gives me the maximum flexibility whether I have the mobile connector included or not.