If I were a betting man, I'd put my money on LaMelo, and he could definitely be it if his game makes a couple leaps forward. Cuz is a 6'7 Point Guard that has the passing down pat, and shows effort on defense, so, coupled with his size, that guarantees that he'll at least be a positive impact defender.
The face of the league needs to be at least a transcendent offensive player, and a good overall defender in order to meet the skill requirement of that role (Bird, Magic, Jordan, Kareem, Kobe, and LeBron all met that criteria. Shaq is the only one that would be questionable.)
With that said, no one in this generation is there quite yet. I wouldn't call Luka or Zion transcendent offensive players, and they both suck defensively. It's a bit too early for Lamelo.