I think ICOs are one source of funding, but I don't necessarily think they are the holy grail. I don't belive VCs will be completely eliminated... at least not the GOOD ones. I do still believe the good VCs add value.
While ICOs are a way to raise money, there certainly are a lot of tradeoffs you make. For example, you now have 1000s of investors that you have a fiduciary duty to vs. just a handful. You now have 1000s of investors you have to manage and communicate with frequently vs. just a handful. You now have to act like a public company at seed stage vs. being able to stay private until you are ready to be more public about financials, growth, etc.