
Bitcoin has been doing 10x almost every halving cycle. With this kind of growth, you could retire on any amount of investment, if you have enough time.
Well, you could, if the world of finance and the financial structure stayed the same.
And things are not going to change a little, they are going to change A LOT, and along multiple-dimensions.
So, the answer to "how much bitcoin do you need to retire" has many answers 1. Bitcoin won't help you retire 2. 0.1 BTC and four years 3. 100,000 satoshis will mean you are wealthy top 1% 4. You are rich, but you can't buy food. 5. It doesn't matter, you can easily retire, if that is what you want to do.
And, these are only applicable if we do not stray too far from average future timelines. Let us run through some of the possibilities, and their corresponding timing.

- Bitcoin is blocked, hijacked, discarded, or other bad financial shift. It could also be because we have no internet, or electricity, or maybe no working computers.
Most of this will not happen, unless you choose to stay in the lowest of vibrations. Or a world that was bombed backed to the stone-age. We are in the age of Aquarius, where it is about learning, expanding knowledge and understanding, so such futures are not likely to almost impossible to happen. That said, there are several ways bitcoin just dries up and blows away. Lets say you wanted to get all the bankster's money in one place, and then make it worthless. Well, bitcoin could be a great honey trap. Most of the bankster money floating around is an financial assets that are about to turn to dust. But, all the money that is able to escape would go into bitcoin. And then you turn off bitcoin. A cunning plan. that might work, if you weren't cutting off your own fingers too. - 0.1 BTC and 4 years Judging by how fast banksters are moving into bitcoin, in less than four years, bitcoin will be worth over ten million dollars. (estimated. Because no one trades bitcoin for dollars anymore) At this point, your ⅒th of a bitcoin will be plenty of wealth to retire. And may even grow faster than you have the ability to spend (as long as you stay away from Needless Markup and buying Lambos) We have gotten to the point where rich people are getting into bitcoin. And after that, it is a short time before everyone wants it, and all the currencies around the world crash to zero vs. bitcoin. So, anyway, any significant portion of a bitcoin will put you into the top in wealth. The only challenge will be whether fees turn your portion of a bitcoin into dust.
- 100,000 satoshis will mean you are wealthy top 1% Bitcoin is now the world reserve currency, and a satoshi is a non-insignificant amount of value. With everyone using bitcoin, or a side-chain of bitcoin, people will be celebrating when their child earns their first full satoshi. There is a lot of people in the world. 21 million bitcoin / lots and lots of people, and then, with the rich and corporations taking a large portion, then most people will have less than a satoshi. But don't worry, groceries will probably be priced in nanoSats. Meaning, your 100,000 sats will pay for enough trips to the store for the rest of your life.
- You are rich, but you can't buy food. This is one of those niches where people have figured out how to win against the "elite". Don't sell them food. Goods money and food money become separate. The farmer doesn't sell to you unless he knows you, or you are known as a farmer too, or something like that. This may happen to gold, as the rots-childs have so much of it. It may also happen to bitcoin. No one will accept the rots-child's money/
- It doesn't matter, you can easily retire, if that is what you want to do. We are actually fairly close to being able to automate so much of our world's enterprises and if we keep the elite from hording all the technology, then each person can choose to work as they are able and as they want to. Imagine if you had a homestead, with an automated greenhouse. It takes care of watering, temperature, killing weeds… and all you need to do is pick what you want to eat. You have not much you need to do to survive. Now, this possibility is quite a ways into the future, but if you are young today, you may see it. I believe bitcoin will come and go before we get to this time. We will learn so much about money and how to work with it, that we will say, bitcoin was a good FIRST step, but we are glad we outgrew it.

The thing about bitcoin and other cryptos is that they are basically only the first step into the realm of good money. And, ironically, the last step is that we learn we do not need money at all.
Somewhere in the middle we learn that money needs to be tied to human worth. As each person has worth, so does the money. And also, each person has worth because of the money they create. This will be really neat to watch.
However, before we get there, we need to remove evil banksters from the money system. And then so many little changes that will mean a huge amount to the future.
Many people think it is too late to own crypto, that the big gains are behind us. But this isn't true. We will see HUGE moves in crypto. So, while you can, buy bitcoin, and if you can't, buy some of the good altcoins. A little bit of bitcoin will make it so you can eat beef while everyone else settles for bugz. Things are going to get much worse for food prices.
In the near future, a million dollars may not feed you, but a bunch of satoshis will

All images in this post are my own original creations.