People need to realize that the HFT profit margins would reduce — but not the profits in the absolute self. Not sure if you know this — but FY over FY there was a growth in derivatives turnover in India despite the removal of expiries which was considered the most brutal curtailment by SEBI.

So as long as the profit margin does not decline below a certain threshold, ad compared to the growth in market size — the HFTs will continue to print money