Yes they will be rendered useless when it hits the same DAG as the ETC DAG which made everyone discover that they were at the end of life.

I didn't really do a specific calculation but those ASICs most likely never ROI for anybody, especially the 2nd batch which was more pricey after they found out that ETH won't fork to a new algo to stop the E3.

Will be interesting to see how the hashrate changes. We will finally find out how many of the E3 Bitmain actually produced. Will it be profitable for home miners? Probably not, not unless we get >$250 price.