I would for sure re-sign him. After tearing the same ACL twice in about a year and a half, it is unclear if he will ever be the same, and you worry about re-injury risk, but I sure as heck would not bet against OBJ, and he fits this team and its offense like a glove.
If Beckham was apparently willing to take a bit of a discount even before the injury, you have to think the Rams and him can arrive at a mutually agreeable number now - with another ACL tear, I am not sure how many suitors will be out there offering him big money and/or term. With a baby on the way and enjoying LA, you have to think he'd like to do the rehab where he is comfortable.
I really hope the Rams do right by OBJ, show faith in him, and offer him a fair deal. What is fair, of course, is to some extent informed by this new injury risk and concern. But he's still a great receiver with real value. I have faith a team like the Rams, with the culture we have here, will not turn around and try to screw OBJ because of this unfortunate incident. My heart broke for him when I saw him go down non-contract. He was an absolutely huge part of this Super Bowl run. And but for the injury, he might well have been Super Bowl MVP. OBJ was absolutely killing it, and you could see him truly enjoying the moment, thriving under the brightest of lights after such a hard time in Cleveland, which was great to see. That moonwalk TD celebration was amazing!