In the $1.7 trillion world of exchange-traded products in the US, one lonely corner of the market has received outsize attention lately: the so-far tiny realm of actively managed stock exchange-traded funds.

Such funds held just $1.5 billion, or 0.08% of the assets in U.S. exchange-traded products recently, according to researcher XTF Inc. But dramatic change could be coming, as big companies jostle to get into this business and the regulatory dam holding them back from certain new approaches appears to be getting leaky.