ICO's are dependent on ETH.
ETH is going to try to solve their scaling problem (Cryptocats, lol), by attempting a hybrid Proof-of-Work and Proof-of-(mis)Stake system. This hasn't been done before, and if Money Skeletor Vitalik screws it up, it could lead to a lot of problems for everything built on top.
Not exactly a position I'd want to be in. Besides, a lot of ICO's are complete cash-grabbing muppetry - and we've seen our share of exit-scams using them. Will ICO's totally go away? No, not in concept, but there is a very real risk that ETH might lose that market with their scaling attempt.
The long tail of dead altcoins will grow, that's for sure.
Supplemental Reading - Why ETH's "Sharding" won't work -
https://medium.com/@StopAndDecrypt/the-ethereum-blockchain-size-has-exceeded-1tb-and-yes-its-an-issue-2b650b5f4f62(or EOS, or BCH, or... most alts)