No i dont think bitcoin will totally rule over the world .it will be totally different and its limitations will be more than 21 million .all the government will jointly accept and i am sure that it will not be bitcoins at all.
It will just take some time for the bitcoin to be the most popular currency.
There are many steps ahead and Bitcoin has to wait in order to be adopted. Many Bitcoin investors, such as me, believe in the future where Bitcoin is the main currency and that visionary is more precise after every year.