It's possible but it will not guaranty success, Dexage has done that they fist held ICO then when they failed to get more funds they shift to IEO, possibly using a portion of the ICO funds to get listed in IEO, they are lucky to get funded on both but it's still will go to the kind of project and the credibility of the team, ICO and IEO can succeed or fail if they do not have a good platform to back them of.