You make the solid case....there is no need for more than 5 seasons. They can’t take Krese on next season, maybe even drag it out with Terry Silver possibly coming back (maybe Mike Barnes?).
Frankly, they can drag the All Valley showdown to season five if they want. They have enough storyline with the kids that it can get dragged out. Don’t forget they have left it hanging out there about who Miguel’s dad is. Maybe Terry Silver? Maybe another baddie entirely? Ive read a theory that posits Miguel’s dad could be a baddie played by Essai Morales (I’m not sure where they take that casting from, but I like it). They have already shown they can develop new characters pretty well.
Maybe season 4 ends with the All Valley, but also sets up a new baddie on the scene that will challenge Johnny and Daniel to hold it all together and push through.
After that....head for the damn sunset. A show that’s come out of no where and done it at great speed shouldn’t be tempted to hang on for 7-8 seasons. Good news is in the streaming world they are in those that bankroll are not as interested in holding on to something. So go out strong.