Oh really? How would the minority SegWit chain even get to retargeting without another hardfork? Difficulty is adjusted after a certain amount of blocks, not after a specified time period. And the minority chain would take months to get to that change in difficulty even if miners never dropped out, which they definitely would after losing so much money.
Retarget at 1/4 the hashrate would take 4x longer. So? You think relatively slow blocks for a month longer would make a 20 billion dollar industry jump ship to something they have no confidence in?
I guess we'll find out, but I think that when one chain takes forever to get a tx through, that will pretty much kill it. Especially when they can just switch clients and get back to normal.