A new BIP being discussed on the Bitcoin-dev mailing list is aiming at making variable Bitcoin block size depending on the fee the sender is willing to pay, the BIP is aiming at making the block space small, decrease the impact of spam transactions, balancing fees with smaller fees increasing in a higher percentage than higher fees, allow larger block size if the sender is willing to pay for it, allow wallets to display the amount, and price, of free block space left and allow senders to have more control on their fee/priority structure.