Can your ears ever pop during flight hard enough that you never get your hearing back?

Possible. Possible but not common. The same thing can happen during a dive. This would be related to leakage of fluid from the inner ear because the oval window or round window have ruptured... A perilymphatic fistula. This is an ENT emergency. Acute hearing loss should always be evaluated... If it is related to nerve injury it may be irreversible if it is not treated quickly.