The cessation of coin production likely won't happen in any of our lifetimes.  Contrary to what you wrote, it isn't too expensive to mint coins (in general).  In the US, this is true for nickels and pennies but not the other denominations.  And as someone else said, precious metals will still be highly valued and so people will still collect coins, even if they were to stop being minted.

Look at the newspaper industry.  Look at stamp collecting.  The world is a tough nut and manages to keep going despite technological advancement.