Uchiha powers are genetic, Nara powers are not (besides maybe their intelligence).So umm if Sarada gets married it won't be to an uchiha. Isnt there a possibility that she marries say someone from clan and changes her name to sarada nara thus ending the uchiha clan and making a more powerful nara clan at some point
So even if she married Nara, the kid could unlock a Sharingan since there'd be no specific gene competing with SG potential.