Okay, but the real question is: Are Beth, Morty and Summer called Sanchez now, or are they still Smiths?
Okay, Since there’s no canonical answer, I’ll give my headcanons instead:
Beth reverts back to Beth Sanchez, since she never got to use that name as an adult, having married Jerry young.
Morty remains Morty Smith because he’s still attached to his dad a bit.
Summer becomes Summer of House Chainkiller, First of her Name