Bitcoin is already in the state of being a well recognized currency. If it gets recognized in all the countries then one thing I could say for sure is a HUGE increase in price. Bitcoin might increase at a speed of $1000 per day which is not a big deal for BTC. Mass adoption of Bitcoin will take place and there will be huge BUY wall in the market. Since many number of people will join the market the chances of increase in transaction fee might also become high. BTC will be stronger than ever as there will be huge number of population supporting BTC.

what will happen?
of course there will be a global crisis that will happen to every countries in the world,
why global crisis ?
because the whales holding it for more than 'normal' and 'average' people.
most of them holding it for more than 0,5%,which mean they can manipulate it as they wish.
ok lets talk about the fact,
it will never be a real 'currency' replacing a FIAT,
they can regulate it but it will never be a real currency,at best it will only like this.

If all countries will recognize Bitcoin as real currency, I think there will be a scarcity in Bitcoin because its supply is limited and the price of it will be very high due to limited supply but high demand. Aside from that, many businesses will prefer Bitcoin as a mode of payment and the government would push the regularization of Bitcoin because they want to get taxes from it.

Im not against in making bitcoin legalize in many country. but this will the things is, when bitcoin will be legalize in all the countries demand will suddenly increase and the price also increase with a limited supply of 21 million BTC. Miners will have a huge profit out of it, there will be increasing of Cyber Market selling and buying Bitcoin many exchange will exist. Fiat money will be left behind and drop off by many people who wants to have bitcoin, bitcoin price will then increase about 10,000$ until people realize what are happening in the market that only big holder can manipulate the market. Then people will stop buying it, drop it, switch to fiat again and bitcoin will left behind, and that will be the born of first bubble in cyber world.

in my opinion it is fine that bitcoin will remain as what it is today. It is good to know and Im very excited that bitcoin are gradually adopt by many merchant today but making it legal in all the countries are very risky for now.

The price of BTC will most probably be more than 10K once all countries  will recognize it as currency. But not just BTC but most of the alt coins will also be huge.

If every single country of the world will adapt and legalize btc the surest thing to happen first is a great surge in its value. More people/investors will buy btc and time will come that an average person cannot afford it anymore. If that will happen and you're one of those early btc holder who are now millionaires, well then you will be billionaires by that time.

Different countries, different currencies, different monetary policies. Some countries consider Bitcoin as an asset and others as currency and based on a country's definition of Bitcoin, tax policies and regulations differ.

If all countries legalize Bitcoin, worldwide legalization then obviously there would be worldwide regulation. Bitcoin is already a global currency, but this worldwide acceptance would push it further to the extent where governments might agree upon a common standard set of tax policies/regulations/legal framework to be enforced on Bitcoin usage. Would that be good? Not likely. Licensed centralized exchanges, governments would want to monitor cross-border transactions using Bitcoin, and many more rules might be enforced on Bitcoin users. Worldwide legalisation would definitely boost Bitcoin adoption, price would skyrocket, but too harsh regulations would take away the financial freedom that Bitcoin offers.

A hyperbitcoinization event is preferable over enforced regulations.

http://nakamotoinstitute.org/mempool/hyperbitcoinization

PS: IMO it's highly unlikely that all governments would legalize Bitcoin. Secondly from a technical perspective, we have to see how Bitcoin is going to handle transactions when around 20 to 30% of world population starts using it.

Indeed! BTC will be taxed to death! That's the reality of gaining too much popularity and demand. Very interesting answer. Thanks!

The dollar that is key currencies turns into Bitcoin.
The  legal currency does not disappear as far as there is a country.