If Ohio State has 3 losses, they could very well get in the NY6.
Look through the standings and remaining games, and you start to run out of 2 or fewer-loss Power 5 teams, with the other teams that will lose this weekend and in the conference championships. None of the Group of 5 teams have any path to to get ranked as high as 12 (except maybe UCF), so there will only be one Group of 5 team in the NY6.
There will very likely be multiple 3-loss teams to pick from for the last NY6 slot, and Ohio State would have as good a resume as any of them (already assuming Auburn gets in to the NY6 as the highest-ranked 3-loss team, probably ranked ahead of some 2-loss Power 5 teams as well). I think Ohio State would even stay ahead of Washington if Washington wins this weekend and stays at 10-2 (Washington is already eliminated from the Pac 12 Championship), but that would be close.