Re: "disappear forever. Will it happen with bitcoin ??"
" I expect Bitcoins might be traded in 100 years, just as Penny Blacks are after they ceased to be carried by anyone's need to have letters delivered"
You could be right, but the fact they're intangible makes them an awful lot less interesting in an album, makes them harder to show off, and being digital they're not going to need special love to stop them degrading in air/light so their perceived 'value' as a collectible may be limited. How many people show off Win 3.1 which could be a 'collectible' in some senses? Certainly a few, but enough to be a market?