So if I get it right..by updating the code of any coin you create a hard fork and u don’t want a hardfork cause of the mining so u put another layer on to top of it!
What about the premined coins?
Bitcoin doesn't have any premined coins.
If you are asking about altcoins, then you should probably ask it in the altcoin section of the forum.
Or when it’s all mined?
Are you asking about when the subsidy ends? More than 110 years from now?
I'm not too concerned about that, we'll all be dead by then, but the intention is for the process to continue with funding from transaction fees alone.