Well i mean the price would most probably rocket to the sky so in my opinion i would start buying as much bitcoins as possible when i would see that the price is going up really quickly
Don't you see a logical problem here? If Bitcoin replaces all the world currencies, Bitcoin will no longer be exchangeable for another currency, hence the "price" is unlikely to skyrocket. What might be skyrocketing is its purchasing power. Stop using fiat as a reference for value, since it's a very bad benchmark.
In case that happens - and I seriously doubt it will happen in my lifetime - I will simply live on and use my Bitcoin to buy the things I need. What else am I supposed to do? Jumping out of the window, screaming "Bitcoin won!"? No I won't do that. Nope.
ya.ya.yo!