There is always such a possibility. I like IEO's and trust them more than ICO's, but only if IEO is conducted on trusted exchange, for example Binance. But even then you can be scammed, as no one can guarantee you that this or that project isn't a scam. Everything can happen, even on a major exchange.
IEO can help from the investor's point of view but what about technical development of project? I don't think conducting IEO from Binance will help projects will technical aspects too. So it is not always possible that IEO will success, they do have more success percentage than ICO but they are also not full-proof.