I think what it proved is that the Cowboys can be "among the NFL's best" when they play well. If they're on their game, they can play with anybody. They certainly showed that on Sunday in a game that wasn't nearly as close as the scoreboard indicated.
What they have to prove now is that the team that played on Sunday will be the real Dallas Cowboys going forward, every week, consistently. If they can do that, I think they can play with and defeat any team that remains on their schedule.
But it will take that team we saw on Sunday, one firing on all cylinders. Offense, defense, special teams.