I am absolutely sure ICOs will continue to exist even beyond the year 2020 as long as these ICOs projects has a clear road mad and will impact positively to the investors or people who understood what the project is addressing in the social economic well being of the people.
For example, there are many cryptocurrencies out there with different features for different users. A brief look on few of the features includes
Bitcoin.
1.The largest and most well-known, this is the cryptocurrency that really kicked off the revolution. Its market cap (MC) is around 30B USD, and it has reached 350k transactions per day on busy days. The currency has an upper limit on the number of possible coins (21 million).
2.litecoin.
This cryptocurrencys main feature is that it is much faster to transact. Since each transaction takes so much calculation, BTC transactions take upwards of 10 minutes to confirm. This is not feasible for paying on-the-go. LTC gets the time down to about 2.5 minutes, though that is still much longer than the seconds it takes for credit cards or cash.
3.Etheruem
ETH is the second largest cryptocurrency by market cap, sitting at about 8B USD. ETH was originally designed to be a platform and not really a cryptocurrency. The transaction time is on the order of 1015 seconds for confirmation, which is a huge improvement. ETH are also released every year, so there is no hard upper limit of ETH like with other cryptocurrencies. This means that not all the coins are in the hands of early miners. Etc
There are many more cryptocurrencies with deference features that people get adopted to it uses on daily basis.