Ethereum succeed in making itself a need for other people, in this case ICOs. That is why it will always go up from now. And with the PoS around the corner, supply will be capped, and price will pump crazily.
you are indeed true about the first part that the ICOs are the only reason why ethereum went up in the first place and they actually are the reason it stays up for now.
but you are wrong about your second part. it can not last forever. you can't see new ICOs start up every day and still be successful enough to gather that much money. it will stop at some point and be limited to 1 or 2 every 6 months. and on top of it all the ICO dumps will crash the price.