It's too early to say IMO. The Bears are literally one of the best teams in football. Colts have lots of injuries too. But your point about the defense and the O-Line is accurate. 6 may be ambitious, but I think they'll win 4-5.
I think Luck had a pretty decent debut, even though he had too many turnovers this week. Donald Brown needs to learn how to catch a short pass for crying outloud too.