Technically, mining of Ethereum will continue as long as the Blockchain exists.

According to the terms agreed by all parties on the 2014 presale, Ether can be mined up to 18 million every year and the yearly issuance if fixed.

About 72 million Ether was created in 2014, and since then, the number of tokens are increasing.

“Ethereum Foundation” expects that eventually the rate of new tokens created every year would reach the average amount lost yearly (by misuse, accidental key lost, the death of holders etc) and there would reach an equilibrium.

Also, Ethereum is expected to be switched from Proof of Work to a new consensus algorithm, called Casper which will have much lesser issuance amount than the current one in the near future.