Well, let's not forget that BA has been charging for business class seat assignments for some time now, so arguably they've already started down this route. I could see a further unbundling of ground services (lounge, checked bags, priority security) like the "lite" fares cited above, but inflight it gets a bit more awkward to separate out those who get a full meal service vs those who have to pay for each glass of wine, and that also cheapens the experience for everyone.