Will they go under? Can they survive on half the amount of income?
answer is no, probably they won't survive, because they will get much less than their fees
so thing that they will do, is probably to switch to other alt coins, or just quit their jobs and no mor mining, but that would be horrible news for bitcoin
The chinese miners will develop a next generation miner. Which will be profitable after the halving.
They surely will not used an outdated S7 miner for longer then 1 year. Altough i am not sure if the S7 will be profitable after the halving.