Believe me I am one who really would like to get excited. The potential is there. Can't help but also wanting to be cautious (not negative, just cautious)
So it depends on how you ask the question
Could they?
Of course they could, they have the potential, Any Given Sunday, etc. They have a better chance then other teams.
I'd be more inclined to put my over/under line at about 18 or 19 points. Meaning at or around 18 or 19 points, they are doing their job. Under or over that amount, they are under or over performing
While I love what's been going on the last few weeks, let's remember that the 49ers are a team that's pretty broken right now and any success they have I'd say they are overperforming (honeymoon phase?). And the Jets? They are on par to be the statistically worst defense in the NFL (so says a Yahoo Sports report I just listened to).
Proceed with caution
(And if you're curious, I hang the over/under for our defense at 13 or 14 points here. I expect our offense to be able to deliver 18 or 19 points any game, and our defense to be able to hold the opponents to 13 or 14)