This is already being done, to a limited extent.
Flybe has a premium fare, that I believe is fully flexible and refundable.
Meanwhile, Air Berlin has their "Silver Card" which for a small fee, or the requisite number of status miles, allows changes to reservations without fee, dedicated check-in and some other benefits. In Germany only, I believe they also have some sort of further enhanced business product - but don't quote me on that.
I'm inclined to agree that some carriers, probably including these two will go down some sort of business class enhanced service at some stage. Strange how life goes full circle.