In 10 years, when BTC is mainstream what % of people will own 1 BTC
Not many. By then, 1 BTC will be so expensive it would be like purchasing a house.
Not few people (more than 0.3%) have money to buy a house.
I guess would be more like buy certain luxury items, that really few people can afford
if bitcoin replaces all fiat, it'd be easily worth 20 million by todays standard.