No, bitcoin cannot kill income tax. Yes we don't have income tax to those people who are earning bitcoins. But many people are still working in a company and we're bitcoin earners are just few. So income tax is still there and if that happens each country's economy will fall down.
Bitcoin can't kill the tax, because we do our fiat money transactions via centralized exchanges which are directly in relationship with governments and financial institutions of the state. That's the reason.