Reigns doesn't need to turn heel, he just needs to keep acting like a badass. You don't need to be a heel to be a badass, actually, badass faces is what we need.
Naw man, he already turned. If he was a real babyface he would have shook Sheamus' hand after the match and gave Del Rio & Rusev hugs. Maybe even kisses. Instead he acted like the most vile hateful heel I've actually ever seen.