A few things has to happen.

- People realize BTC's flaws - slow and high tx fees. Like it makes headlines news.
- USD to alt gateways. Make alt coins easier to buy with USD. I wouldn't even be buying btc to buy alts if this were the case.
- Adoption of other cryptos.
- Some major FUD that will cause a great crash equivalent or greater than China bans.

All these combined then maybe.