When Football Outsiders recapped the Week 6 games, they specifically mentioned two NFC North teams (Packers over Chargers and Vikings over Chiefs). These were both close, one score victories by two NFC North teams, but according to Football Outsiders's advanced metrics, neither game was as close as the score suggested. The Packers significantly outplayed the Chargers in their win, and the Chiefs significantly outplayed the Vikings in defeat. The Chargers looked better than they were because they ran almost twice as many plays as the Packers (which in itself is a problem) while the Chiefs were hurt by penalties and every big play went against them.
It's too early to say the Packers are guaranteed to win the NFC North, they've only played one divisional game so far, but they're up by three games already and their only significant competition (Vikings at 3-2) are ranked as the 26th best team by Football Outsiders after Week 6. But it's fair to say that they're in great shape to win the division.