What u think?

"We did add an extra feature to the SC1 unit that would allow us to invalidate the Bitmain hardware without invalidating the SC1. The community would need to choose to adopt a soft-fork (it's not something we could just magically activate, we have to change the hashing algorithm slightly), and then we could get rid of this cycle of Bitmain hardware. Of course, they could just create another round of hardware (likely taking ~3 months). And, it would hurt Bitmain customers more than it would hurt Bitmain. Bitmain has already sold around $20 million of non-refundable hardware. They have made their profit, and a soft-fork wouldn't change that."

From Sia Dev team
https://www.reddit.com/r/siacoin/comments/7r4spy/dev_team_thoughts_on_the_bitmain_a3/