I think yes they can stay in a long run but doesnt mean that they are always getting success just like an ICO now it just like a bubble that nobody wants to trust because it always gone whenever they take the money,IEO is only hype now because it was trend but okay let we see what will happen on it in the next year.
The fact is that today there are a lot of new ideas and projects that professional developers want to implement. I do not take into account fraudulent projects. But not many of these ideas will be able to use IEO, because we know about the harsh conditions of this procedure. Anyway, most of the new project will pass through the market of ico companies.