Probably transaction fees? There's no reason a blockchain must be self-funded through proof-of-work mining.
To my understanding, the expected future state of Bitcoin is that the role currently filled by miners will be replaced by transaction processors who take a fee to do the work.
It's not about the mining!!!! Block chain is about having an immutable, non-repudiatable transaction record.
Block chain is a wheel.... guess what, wheels have uses far beyond the Pharaoh's war chariots. Like, you know, bicycles and automobiles. Stop conflating block chain and crypto-currency.
To my understanding, the expected future state of Bitcoin is that the role currently filled by miners will be replaced by transaction processors who take a fee to do the work.