What exactly you mean by this? IDOs and ITOs never really went away. They just changed their names to IEOs, IDOs and such, and there are private sales as well.

But first big wave of ICOs that were unregulated and public for everyone aren't coming back in a similar  because huge portition of the successful ones got sued, many of them were outright scams and some of the "CEOs" got even jailed for them, because they either stole the money or sold them as "investment". But again, you can see plenty of tokens launching in DEXes all the time. They just don't use term ICO, because why would anyone want to do that? They are flying under a radar so officials doesn't seem to be paying attention of all the scamming happening in there

There's one thing that ICOs did that will probably affect the whole investing culture. They showed us that if there's an early investment opportunity that has easy access for everyone, money will flow in. I am guessing there will be an easy access for everyone to buy actual IPO stocks in the future, because there's obviously high demand for that. It doesn't even really matter if it's decentralized way or not, it's still a step for equal opportunities for everyone.