If it is hard coded then it should not be possible to change it. Ever! Is there anything that can not be changed if needed? I need some more bitcoins. Would you change the protocol for me?
Even something hard coded can be changed, including giving you more bitcoins. The process would be:
1) Obtain a community consensus on the change.
2) Develop patches to support the change without activating the change.
3) Wait for significantly more than 50% of miners to be running a build with those patches. (At minimum. Obviously, if possible, wait longer than this to minimize disruption to clients and services.)
4) Pick a block to begin the change.
5) Develop patches to make that change at that block. (Or trigger on an event.)
6) Wait.
This would be a painful process that would likely be at least somewhat harmful to at least bitcoin's perceived stability. So I doubt you could make it work just to give you a few more bitcoins. Perhaps if you gave me a few more as well ...