Icahn, of course, owns a majority stake in an independent oil refiner and loved Trump's pick of oil-industry-best-buddy (and ethanol foe) Scott Pruitt to lead the EPA, so he's not an independent observer. When Priutt was named to head the EPA, the price of the Renewable Identification Number (RINs), which are the currency for ethanol trading, cratered. They have since bounced back, but there are still reasons for the ethanol industry to fear Pruitt's effect.
As for what the future might hold, let's listen to what Trump said about his then-rival Ted Cruz in the Iowa caucuses, calling him out as a tool of the oil industry: "And look, I'm not really blaming him because he's financed by oil people. The oil people don't want ethanol, it's very simple... Your ethanol business if Ted Cruz gets in will be wiped out within six months to a year. It's gonna be gone." Only now, instead of Cruz being controlled by oil interests, it's Trump himself.