It all depends on the attention these attacks get. Now that they've had a tangible effect on the news cycle, creating concern about the safety of US energy infrastructure, there will be more incentives for the Government to hunt them down and get credit for doing so.

I think I read somewhere that China based attackers have already penetrated networks of major US infrastructure systems but didn't do anything because whats the point of wrecking havoc now? Better wait for more opportune times.

Which also seems to indicate that this may not be a Nation State... they would be after a bigger prize than some bitcoins.