I bet that in 5 years from now (even faster) Bitcoin or other cryptocurrency will join too.
That is highly unlikely.
First, Bitcoin would need to become a reserve for a country.
i can see this happening easily in soem corrupted country, that are very poor, if bitcoin will have big adoption in 5 years
does countries like liberland count for this? i doubt but maybe
Someone's backyard is hardly a country.
Bitcoin could join in one day; if we get our goal of proportional growth as block reward goes almost to zero.