Football programs like Carver and Parkland could be rebuilt fairly quickly if open enrollment was not a thing in Forsyth County, but because it is, those schools will need a miracle plus some to be competitive again at a state championship level. Also, because they are magnet schools now, high level athletes probably aren't going to go there even if they have a good coach, because there will be a good coach somewhere else with better competition, like EF, Tabor, WF, Reagan... etc.
Open Enrollment wouldn't help NW Guilford out much anyways, I don't think. What you should be worrying about more is when the county is going to build another high school in the NW part of the county, probably within the next 5-10 years.