When one asks others about God's omnipotence, they mean all powerful, however in the church we have certain beliefs that we do not believe god will or even can change. For instance from "The Family: A Proclamation": 
 
"Gender is an essential characteristic of individual premortal, mortal, and eternal identity and purpose" 
 
So if gender is eternal, then God cannot change your, or his gender. If so, then God isn't omnipotent.