If in a few years Bitcoin becomes the "Norm" worldwide thus eliminating the use of state backed currencies , what would the "price" of a bitcoin be?
"Few" years? You're getting a little ahead of yourself buddy. The network wouldn't even be able to handle a small fraction of the transactions taking place in the world daily. Heck, even if you limit it to just a small fraction of online transactions, it still wouldn't work. And that's just the tip of the iceberg. There would be infrastructure, economic, political, etc. issues to tackle.
If we were to assume that this will happen though, imagine
all the money in the world being represented in just 21 million Bitcoins. We can't really come up with an accurate number, but one Bitcoin could easily be worth as much as quadrillions or even quintillions of USD today.
I personally don't think Bitcoin will ever eliminate official currencies, but that's a different discussion.