You need to realise that in the past Bitmain built these miners, mined with them for months and then when the profits were decreasing they finally decided to go public and sell the miners.
This is what happened with the E3 that bitmain released, the very first ETH ASIC. They pretty much released it after the peak. How long did they mine with them prior? Probably for months. And this explains why in late 2017 we had a huge difficulty jump that nobody could explain.
So just because they are building ASICs for it doesn't mean that it has to be always profitable.
Right now im sure there is alot asics are mining at speed 2-2.8ghz on network.If you start seeing these asics soon for sale will not surprise.