Ethereum's smart contract system is always and will mostly be always used ICOs of upcoming projects.
They just created a system that makes it so easy for anyone to start crowd sale funding.
Yes that might be a huge factor in its price as people who are interested in ICOs keep buying and holding/investing eth. And as long as there are new projects, it will continue to have value.
But what if all ideas are gone
It's impossible. Ideas never run out. Everyday the human brain comes out with new ideas in every margin of life. Not sure ? Compare our world today with 10 years ago.
What if it's in the field of technology which have endless opportunities ! Not gonna happen anytime soon.
Plus if we just take the crypto world into consideration, we still need a lot of development to integrate it into every aspect of our life. We need shpos, hospitals, schools, universities, pharmacies that accept btc.
So clearly ETH it's a long-term project.