Depends entirely what you buy, whether it will keep more than a few years,
and what it would be worth so far ahead is quite imposwsible to predict sensibly! Get a recommendation, buy more of it than one bottle, don't keep it so long, but even then you have to be careful it doesn't go off by trying it regularly. Would be an absolute waste of money if you don't do all that (otherwise millions of others would be doing it if it were so easy & safe).
Top quality vintage wine has to be stored in a wine celler at the correct temperature and humidity just putting it in cupboard will not do.
Some wines improve with age some go off you need to know what you are buying.
It's not as if I'm really planning to do this I just wondered. For arguments sake lets say in 50 years time I get this bottle of wine out of the cellar, wouldn't someone have to buy it before opening and tasting it?
Sounds the sort of 'investment' that might go down well.
But get decent advice on the year/vineyard/etc., not all years are declared vintage.
I can't see how a potential buyer can expect to open and try a single bottle before buying, but I'd suspect a single bottle from a seller without a rep might not attract most interest.