So in the future, fiat currency will become digital only and cash will completely disappear. Credit cards will also disappear. People will be implanted with chips that contain all their information and they'll need the chips when buying or selling goods
Dude, those implanted chips you are saying only exist in a Sci-Fi movie. Stop relating our
real future with those in such movies for those are merely wild imaginations.
How would bitcoin coexist in the future with this method of payment?
At the beginning, bitcoin is already coexisting with the fiat money so even if bitcoin gets accepted worldwide, it will be the same.
Will it get accepted as a second currency?
Actually, I personally do not know. And as for my opinion, it has no sense at all if it will be treated as a second currency. Bitcoin will still be bitcoin. We can use it in any transaction so why treat it as second currency?
What about other crypto currencies or bitcoin forks?
What is your clear question regarding those? I cannot answer such question correctly/accurately if the question is unclear. It will just raise confusion.