I am sure Icahn has smart tax lawyers because one can be sure New York will track when he is in New York to see if he is doing any business there and whether he is truly becomes a non-resident.
They hounded Rush about his residence for years, and for all I know may still be hounding him. He had to keep every single airline ticket and hotel receipt to prove his whereabouts for all 365 days of the year, lest they claim he exceeded the threshold and was therefore a taxable NY state resident.