Reading into this, I think all this really only effects the base level contracts with no roaming extras. With whatever network I've been with, I've always subscribed to the extra roaming package. In reality, I've often thought that the "per day" model might even have been cheaper based on the amount I use mobile data abroad anyway.
There are some people on base level contracts that might have to pay for something they once had for free but I'm not sure this news is as costly to most as it first appears and depends on what package you normally sign up for.