If you are retiring in 15 years or more its well possible that 1 bitcoin can be enough to retire on even in a first world country. I wouldn't put all my eggs in one basket though and rely solely on that, I would still look at other options just incase.
I think 1 btc would be so much less if you were expecting a glamorous life or all the necessities could be bought. If you want your life to be rich then you need more than 50 btc to be able to get a good life. Then make that target and discipline