The chances of becoming main stream of payment within 20 years is 100% possible..
100% possible? oh boy, you need to prolong your post and add some numbers in order to get pay by signature campaign, don't you?

what a bullshit.
Please be optimist. Now itself bitcoin can be used anywhere with the help of bitcoin debit cards. So, after 20 years, definitely we can buy/use bitcoins everywhere. 200% possible.