Luffy at the beginning of the arc was speedblitzed and oneshotted by Kaido when he was in G4. And that is probably Kaido's human form (i still hope it's isn't). Denjiro and the dukes in sulong form weren't even able to hurt Kaido in a 9 vs 1.
Now the 5 supernovas are against
two emperors and Zoro, Killer and Law are all weaker and slower than that Luffy and certainly not far stronger than those 3 scabbards, especially the dukes in that state. There is no way they can be of any help logically. But they will
Against Oars he was not so usefull, i doubt Oda is going to not give him a 1 vs 1 for something like that.