One of the biggest changes, as far as I can see, is that they have made claims for "free" reward tickets in premium classes much much more difficult, while at the same time introducing or extending the reach of mileage-paid upgrades, one class at a time.
So if you want to fly in J but in a tightly capacity-controlled award class, you will realistlically have to at least fork out for a T class ticket. If you want to fly in F, you must at least have paid for an I class. I would therefore bet that a much bigger percentage of premium class reward tickets will now effectively be part cash part miles. This at least is consistent with the philosophy of protecting the premium classes as BA's strength, and keeping up the yields generated in them.
The other signal from the changes is something that won't affect current members, but will dramatically reduce the intake of members into the scheme. That's the requirement that you have to have flown at least one Tier Point earning flight in order to join. No more examples of people flying solely on deep discount tickets and dribbling miles into their account over a period of years until they have enough for one reward ticket - it must be wildly uneconomical to service these members who by definition are capacity-filling fodder and generate virtually no profit. Again, the emphasis will be on looking after only those who fly full fare or premium classes at least occasionally, but then looking after them whenever they fly.
Every change to a frequent flyer scheme in the last 9 months has generated huge amounts of "I'm going off to fly some other airline now, burning all my XX miles and never coming back to them." When every airline has finished with their changes, all designed to stop the marketing tail excessively wagging the remainder of the airline dog, are these pax all going to stay at home? Or might they just start buying airline tix on the basis of the airline which has the most attractive combination of service, frequency, schedules and fares? Some rational behaviour in the airline market. What a novelty.
As for this example of capacity-filling non-profit-making fodder, I'm sticking with my QF membership, which has already been "downsized" a while ago, which works for me on all my BA flying and which seems a less likely candidate (for all sorts of reasons) for another round of cuts.