[Frogolocalypse]

The technology of lightning, which is not specific to bitcoin, would probably have to be it. It allows atomic cross-chain trading :

https://en.bitcoin.it/wiki/Atomic_cross-chain_trading

I suspect that all cryptos that want to survive will need to implement this technology in their blockchain at some point or another. Already, there has been chain trading between litecoin, decred, and bitcoin that I know of. I'm sure there will be more going forward.