The European Commission obviously only has jurisdiction with the EU, so with a bit of luck this'll be limited to EU member countries only. On the downside, this means bidding a fond farewell to the ex-WAW fares, although the ex-ZAG may survive. On the positive side, it'll make booking the I-class BA fares ex-LIS a lot easier, although that bottleneck seems to have been removed by BA earlier this year anyway (possibly by the imminent EC action).

Although the SITI-like codes may go, I doubt airlines will completely abandon regional pricing simply because they have to offer equal access within the EU. The EC can enforce the equal treatment of sales out of WAW for all EU customers (and not just for those in Poland), but my understanding is that it's still legal for the airline to differentiate between EU and non-EU sales. Essentially the EU becomes the "country."