To start, Banks and governments will fight to prevent its use as a currency or they will co-opt it to more completely control the movement of money.
Yeah, and how is that working?
Cause I see governments legalizing's Bitcoin everywhere but when I ask bitcoiners if they want to use it as a currency 99% of the responses are "My previous, why spend it, it can be 10000% after the halving, it's stupid to spend this investment, my precious, give it to me".

They will have to sell bitcoins to have cash but how much they will sell from total bitcoins they have will be different by investors. Investors who have strong finance and good finance management, will don't need to sell bitcoin because need of money to use. They already reserve cash to use without need to sell bitcoin.
With small investors who can bet all in bitcoin, they have bad capital, financial management and they will have to sell bitcoin even before a halving. Sometimes they have sudden need of cash and can not hold their bitcoin.
Have good financial and capital management will hep us to maximize our chance to get profit.