Snow and Charming are not going to age. I think there is no chance that is going to happen. That is one of the consequences of being stuck in the curse, that they lost that time with their daughter and it would be worse i think if they were already 28 years older and just lost that time all together. They would be in their fifties. I think that they will remember their real world selves because we saw Charming after he got his memories back driving a car. He drove his truck back into town to find Snow and he wouldn’t know how to do that if he didn’t still remember stuff.