The line that is most likely to cause the class to change their prediction is:
“Lip-lip ignored the challenge. He was no fool himself, and whatever vengeance he desired to wreak, he could wait until he caught White Fang alone.”
This line suggests that Lip-lip is not deterred by Kiche's attack and is still planning to seek revenge on White Fang when he has the opportunity. It implies that Lip-lip's intent to attack White Fang is still very much alive, contradicting the class's prediction that Lip-lip would leave White Fang alone for good.