What is your expectation of bitcoin ?
If all countries legalized Bitcoin, the Bitcoin price would be more stable than it is today. Of course we will find it difficult to see a bull market as we feel today. And while currently Bitcoin is not legal in many countries, I see no restrictions for the use of Bitcoin so far. We use Bitcoin so far it's still smooth, I haven't found a blocked Bitcoin wallet. Of course if Bitcoin is legal, and certain rules are in place, I'm sure there will be high taxes here.
As you said, the legalization of bitcoin will help bitcoin become more popular and used and can be considered as a legal means of payment along with fiat, this is a positive but also has a lot of downsides that many of us will not like. That is it will become more stable, which is probably the worst if that happens. Volatility is a unique feature of bitcoin that no other asset class has ever owned before, if it becomes stable and unprofitable, then I think bitcoin will be no longer interesting and many people will leave the market in search of a more attractive market.