Investing on Ethereum if it will try to start an ICO will be a risky move, I guess. But knowing Ethereum for a long time, I came to love this coin, and I will risk for this coin. There are lots of ICOs that are now scams, and I am sure that if Ethereum will be an ICO again, it will be successful.
You will invest in Ethereum's ICO if it were launched today because Ethereum has already a name. It is the most solid among thousands of altcoins. It has been occupying the spot next only to Bitcoin. But the question is, supposed you haven't known Ethereum yet or there was no Ethereum yet and then it just came out right now, would you still risk your money to it?
I doubt Ethereum would be successful if it were to hold an ICO right now. With the current reputation of the ICO market there will hardly be a project that will gather a big amount from investors. The investors are already fed up with scams and crap crypto projects.