I'm not gonna put a number to it (mostly because every time I go through the schedule, I end up with what feels like an absurdly high number), but I think this team is better than most people realize. I think a top 10 defense and a top 15 offense is likely, with the upside of a top 5ish defense and a top 10ish offense. Those combinations make for very good teams.
The most likely path to downside seems like it's the OL being abysmal. Fingers crossed that it's adequate, because I think that's all it needs to be. The other wild card would be having a tough luck run in that late season gauntlet of divisional games. The inverse is also true, though (run hot and get into a great position).
If Caleb is THAT dude (the type to have a big rookie year - stroud, herbert, prescott, etc. type - something that should be realistic for a prospect of his caliber) and they steer clear of bad injury luck, I have a hard time putting a ceiling on what this team can do, given what is around him.