Is it possible to change the code and add more coins? Yes, will it ever be done? No, bitcoin is now a one trillion dollar project and the developers are never going to do anything that could risk bitcoin in that way, this is why updates are kind of slow as they want to make absolutely sure that everything is OK before they apply an update and the same is true for the supply of bitcoin.

The decision to cap the supply made by satoshi at the beginning of the project is probably the most important one that has nothing to do with innovation, he created an asset that is scarce and that as demand grows its price will grow with it, getting rid of that or increasing the supply will crash the market overnight and no one wants that.