It depends, is the story of HODLERS true or not? Is bitcoin digital gold? Will it be more than that? Might some countries with garbage currencies adopt it as their own currency? Unlikely, but who knows.... The US likes to control people, will they ban possession or just regulate it so much to the point Americans will be out of the game? Possible.. The most optimistic scenarios would entail most of the world using bitcoin, at least the developed world anyway. In that case even having a single bitcoin would make you wealthy. Heck I would say in that pie in the sky scenario (but who knows, never say never) a tenth of a bitcoin could make you part of the 1%. If bitcoin is digital gold and people will be moving out of metals and into bitcoin, that's ten trillion in the gold market alone that could be moving into BTC. Multiply BTC by 20 and I think that's reasonable (optimistic of course but not crazy) in today's dollar terms. So a little over 500k a bitcoin. Again there's no guarantee this happens, but it could. In the third world you would probably need one to retire on, in the US, Europe or expensive Asian countries probably need 4 to retire comfortably.

If you want to be on the safe side I wouldn't retire until you have land and property that can tide you over and the BTC is the icing on the cake.