Duke and Tommy's lawsuit against Rocky
After the street fight these 2 just lost out on a fortune. Being that they are both pretty despicable scumbags, I doubt they just walked off into the sunset afterwards. Duke even threatened to sue Rocky if he hit him, and Rocky did just that. Yes Rocky even assaulted Tommy. All Tommy did was challenge Rocky to a legitimate boxing competition, but after Tommy defended himself after being violently shoved by Paulie, Rocky challenges him to a street fight and almost knocks him out.
In the aftermath of the street fight Rocky would most likely be sued for assault by both these pricks. Rocky sarcastically told Duke "Sue me for what" but the fact is the Balboa name is still valuable. If he got back in the ring his fans would pay to see it, not to mention endorsements. Instead of the George Foreman grill there could have been a Rocky Balboa grill. Rocky could put his name on dogshit, and someone would buy it.
A savvy and ruthless businessman like Duke is sure aware of this, and there is little to no chance he's just walking away, especially after being assaulted. Duke and Tommy now have leverage over Rocky. Most likely the plan would be to offer Rocky a chance to get in the ring with Tommy, and in exchange they would drop the lawsuit. Rocky now can either get back in the ring, and probably profit from the fight, or he has to come up with a Rocky Balboa grill type of product.
With the exception of Adrian's death it's largely a mystery what happens after this movie, but Rocky does eventually come up with enough money to open his own restaurant. If he lost the speculated lawsuit then Duke and Tommy would be milking that restaurant. They both lose out on a huge payday if Balboa doesn't get back in the ring. Tommy Gunn never even got his true payday. Only the Champ gets the multi million dollar paychecks. Maybe Gunn made a million tops for knocking out Union Cane. Gunn definitely hurt his image big time by going after Rocky. Would the fans even pay to watch Gunn fight anybody except Rocky since most of Tommy's fans were Rocky fans? I could see Gunn fight again in the ring, but after a couple fights when it's clear he is not selling out the arena, Duke drops him like a bad habit.
As for Rocky he is obviously doing more than ok as a restaurant owner by the time we see him again in Rocky Balboa. That being said it would ultimately seem Tommy and Duke miraculously decided to be better people, and not bother Rocky anymore