Depends on where you live. If the cost of living in your country is high then calculate that with some statistics on how much a person needs for an average retirement fund. 1 Bitcoin could be enough with an average price of $30k~ish but in major cities and countries, that's barely enough for a retired person. That's why, you need to look at those studies on how much it will cost a retirement fund to become sufficient and compute on how much Bitcoin should be in the future if you're wanting to retire already. But I think many will agree like having 1 Bitcoin and the price of one is $1M.