I hold quite a bit of Bitcoin in time locked addresses until 2020. I am actually fearing that their value will be greatly diminished if Lightening Network doesn't succeed. There are Bitcoin maximilists who'd never hold another coin who are starting to buy RaiBlocks because it has all the properties of Bitcoin but it has 1-3 second transaction time and is without fees. If we start seeing an exodus of Bitcoin believers when RaiBlocks gains momentum, I can't imagine where this is going to go.
Downfall of bitcoin might mean the crash of entire cryptomarket. Who would buy crypto if even the best of them becomes worthless when new better versions of crypto are released?
In future I think we will have many different cryptoes for many different purposes. Bitcoin might be something like gold instead of cash. It will even have smart contracts in future.
Some will of course die, but mostly just shitcoins or coins without proper funding for development.