No they didn't tell him not to come back. They asked him back and he was going to be one of the main characters (The Storm and Nightcrawler relationship was suppose to go deeper, in a friend way not lovers. And Mystique and Nightcrawler were suppose to be in more scenes together) but the actor (Alan Cumming) said he didn't like the long makeup hours. He said he'd do it for a very large amount of money, more than he was worth, apparently. It's a sad loss
He was the coolest character. They should've made some kind of mask that looked really realistic.