Seems that you are thinking so advance that you want to know what may happen to the future, First of all, there is no need for mining Bitcoin because all existing Block was already mined at that year, that is for certain and the only thing possible, but for some rewards, I think newly form projects might still be possible so there is a chance that they could take free airdrops or bounty campaigns if there might be existing in the future because we certainly know that Bitcoin's value will be to the moon by that time and maybe there can still be rewards that may be under blockchain from certain coins or Bitcoin if it will be included in price money for a certain event or competition.

And Enslaving is not the right one, I think it is to be free!