So the cryptocurrency's first generation is BTC (1.0) and second generation is Ethereum (2.0).
Blockchain 1.0 addresses the first generation as Bitcoins and forks. Blockchain 2.0 looks at extended functionalities.
What will Bitcoin do to stay relevant in Blockchain 3.0.. 4.0... 5.0 ?

Bitcoin needs to solve its transaction issues to have any chance at staying relevant in any of the future Blockchain versions. With blockchain projects like NEM doing about 4000 transactions per second, I wonder how bitcoin's 7 transactions per second will compete against that.