Robby and Miguel's rivalry appears to be front and center in Cobra Kai season 5, and that could cause the show to repeat its biggest flaw. After season 4 saw the All Valley Tournament finally happening and Miguel going to Mexico to look for his father, it was safe to say that Cobra Kai season 5 would have quite a different dynamic from the rest of the series. However, the Cobra Kai season 5 trailer suggests that some old plotlines that go back to the very first Karate Kid film will continue to be part of the show.
Despite being arguably Cobra Kai's main characters, Robby and Miguel did not share many scenes in season 4. In fact, apart from the quick exchange during the park almost-fight and the couples' dance battle, Miguel and Robby's paths did not cross during Cobra Kai season 4. That is now confirmed to change in season 5 as Robby will join Johnny in the search for Miguel in Mexico.
The fact that Robby is helping his father look for Miguel seemed to suggest that the long-running rivalry between Johnny's son and his student is finally going to be resolved, but that does not seem to be the case. The Cobra Kai season 5 trailer reveals not only that Miguel and Robby will be on bad terms when they first meet in Mexico, but the two of them will also fight back in Los Angeles. This type of dynamic between the two of them very much resembles that of Johnny and Daniel, and the show could repeat the same mistake of having a feud between characters that never goes away and that prevents those characters from growing. The rivalry between Johnny and Daniel is fun and has been part of the franchise since the first Karate Kid movie, but it is reaching a point where it no longer serves the characters' stories – a problem that was particularly evident in Cobra Kai season 4. Miguel and Robby are walking down a similar path, and continuing their feud in Cobra Kai season 5 could be the wrong choice.
The relationship between Robby and Miguel is complex, and it involves much more than just karate disputes. Johnny's time and affection, as well as Sam's feelings, are things that have placed Robby and Miguel on separate sides, and that only got worse after the school fight. However, given all the time and effort that has been put into Miguel's injury recovery and into Robby fixing things with Johnny, continuing the feud storyline would be redundant at this point. Robby and Miguel have more important things ahead of them, namely reconnecting with their fathers, and wasting time fueling a rivalry would not make sense either in-universe or for the story of Cobra Kai season 5.
Robby and Miguel both resemble different aspects of Johnny and Daniel, but that should not mean that their relationship must repeat that of the senseis. In fact, the most interesting thing for the show to do would be to flip expectations and resolve Robby and Miguel's rivalry right away. That, however, seems unlikely given what the Cobra Kai season 5 trailer has revealed. It remains to be seen how much longer the rivalry storyline can continue in Cobra Kai.