When they get smart contracts fully working over Lightning Network, I fully expect an BTC based ICO. I'm still going to advise against buying it though.
There are several articles and podcasts about why people keep buying into new ICOs and other coins when it has been shown time and time again that there are dozens if not hundreds of coins that simply do not exist anymore and the chance or recreating an investment success that BTC or ETH had is quite slim.
In fact, ETH was really a damn miracle considering all the other alt coins that died before it. There were many predicting it would be a failure on startup. But it succeeded so people think they can do it again... But they forget, that out of 100 alt coins... There was ETH.
To be fair... DOGE is still a thing.
If you are bored and have time, take a look through this list before investing in a new coin or token:
There are 934 official dead projects/coins/tokens.
RE: 2019 will start disappointing