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.
It is only your method to exchange Bitcoin directly through the centralized exchange and you do not know anyone can exchange Bitcoin P2P with you.
While, there are many people know the nature of Bitcoin and take advantage its nature to create many transactions without government tax.