To retire if one BTC gets $1m depends on how many Bitcoin you have got, the kind of job you are doing, the situation of the economy of your country, your age and your responsibilities. For someone that has just one BTC and yet the person is still in their early 30s with enough agility to continue working and making money from other sources, the person might likely not retirer, for someone that is in a country where the standard of living is so much expensive, they will have to calculate how long they can continue spending the BTC that is now $1m before it finishes, if it can serve them through their life time, that's only when the person might want to retire.
Age limit, amount of Bitcoin held, and less responsibility can make some people retire if BTC gets to $1m, for someone that has a very low responsibility and maybe possess like 3 or 10 Bitcoin and is also old enough like 40 years, the person can retire. So, it depends on some certain situations with the individual, before they can accept to retire.
Everybody would be happy to have even one BTC by the time they come such an age - and I agree with you, it heavily depends on the person in question.
And what targets they would want to achieve - maybe they would want to cash out much earlier or for something else, other than retirement..
