2&3: No bankers haven't infiltrated cryptocurrency. I mean, they obviously own some, cunning bastards, but there aren't enough bankers to manipulate the prices. They can buy big and dump once, scare people into thinking it's an unstable bubble, but they cant make a pattern of it. But i'm sure they are exerting political influence in manycountries to ban cryptocurrencies (eg. south korea), and spreading 'bubble' propaganda to scare people from trying to move away from banks. But this is the beauty of cryptos. The power is with the people.

6: Another better altcoin might always take over in the future. More efficient, lesser transaction fees, maybe anonymous (if that is what the people want), etc. But bitcoin isnt done just yet.

7: Because of the decentralized nature of blockchain and the philosophy behind it, I'm sure cryptocurrency is here to stay :)