As unmined bitcoins get lesser, the difficulty and the time needed to mine gets higher. So unless technolgy advances on par with the speed of mining, then we will see the end soon. Otherwise, years or even decades more will be needed.
That is not how it works. The production of new bitcoins is on a fixed schedule. It doesn't matter how many miners there are or how good the technology is. Please read this:
https://en.bitcoin.it/wiki/Controlled_supply