[humbledrone]

It is correct that after 21 million Bitcoins have been mined, other incentives will be required for mining to continue. Transaction fees are the likely choice.

If Bitcoin became a major currency, I think there might be other incentives, too. To speculate: a large government might want to run mining operations to make it more difficult for other governments to collude against them in a 51% attack. Of course if they did this, they'd probably want to pick up transaction fees as well.