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.

Nope: Popping ears doesn't damage ears or hearing as well. In fact, it's evidence that thing are working right, i.e. pressure equalization between the middle ear and outside, which prevents ear damage. If your ears DON'T pop with changes in altitude, and if you also then have reduced hearing or full feeling in the ears that goes on for more than a few days, see your doctor.