The airline is probably well aware of the potential issues - it may well have calculated that any impact is offset by the benefits to it

Now that the issue has been forced, the holdout agencies may well adapt as needed to be able to sell the fares. A short term impact to some flyers may well be acceptable

If required to use an agancy that will not sell acceptable AA fares, then use another airline - until that airline takes a similar stance

I suspect that agencies will be more likely to adapt