I would be seriously peeved if Kenyan doesn't turn up in the league. There are a lot of rivals this season where it's kinda hard to tell where they fit, just because both Cilan and Iris have rivals but no real goal that's accomplished by winning a tournament. Back when just Ash & May and Ash & Dawn had rivals they would either be in the league or the GF.
Now we just have trainers like Kenyan and Langley who show up for these tournaments but don't seem to have measurable goals. Those two are honestly my favorites of the rivals. Kenyan I can't picture doing anything other than the league though,e just reminds me too much of Masamune so I feel like he should show up there. I have no idea what sort of resolution to the plot he could give if he just shows up for his last time outside the league.
Langley just wants to bust Iris, so I have no idea how the writers plan to resolve that rivalry other than some schtick where Langley learns to like dragons and no longer wants to bust them.
I also completely forgot about Bel. She'll be at the league too. I could see her going pretty far, though I don't really care for her. Her whole character is about proving to her father and herself she can be strong, so I feel like she'll be a sleeper hit when it comes to the league.