Togashi already has storyboards up to chapter 430 (probably even beyond 440), and the entire arc is already planned (based on his comments from 2018, iirc).
So, I’m not sure how your prediction will play out in 2025, or if it will happen at all.
Wasn't it assumed that a prince's beast couldn't attack another prince? How, then, did Luzurus's beast attack Fugetsu? This suggests that Melody and Kacho hypothesis may be false, and the bite is from someone else