Can we really argue candy bars and ice cream are the same as a brand new industry such as cryptocurrency?
New alts won't destroy all coins but I could definitely see a massive market crash that makes them all worthless for a year or two before they are reborn.
it would be due to the bitcoiners going galt. they all quit from mass frustration. but even if it crashed and people stopped mining, all it would take is a couple weeks for difficult to collapse before people started mining again. that is the beauty of it. any crash is short term.