It depends on when Tesla actually submits your registration details to the DMV.
My wife bought a new car last month on the 8th, it didn't make it into the DMV system (titled) until the 17th. Her plates arrived on Monday (5th).
I got my X on the 10th, it finally showed up in the DMV registration system (titled) on the 24th.
I just got my plates in for the X... Now to get a front license plate mount.. May need to visit Lowes and pick up some bolts for the no-drill option...