I don’t know about whether the EU as a whole will do something but I think that there are certain elements within it that would strongly benefit from pursuing this path.
First, the European Court of Justice, has staked its credibility on this decision. The U.S. Supreme Court grew enormously more powerful (some say to become the most powerful branch of government), during the Warren Court years, because of its de facto control of the educational system, which is an enormously significant institution in society as a whole. Control over the rules and behavior of company related to personal data, with the ECJ positioned as the (monarchesch) guardian of the common man as against the (aristorcratic/oligarchic), could promote the ECJ to the same position within its own system, a system which has seen its moral authority decline ferociously as the EU infrastructure has become seen to be the instrument of the favorite bugaboo of the month, whether that is distant bureaucrats in Brussels, menacing German politicians and financiers, or rapacious U.S. companies.
By contrast if the Court backs down, or is seen to back down from this decision catering to those same bugaboos, it’s power and influence will be enormously reduced, if only because people will take their complaints to the European Court of Human Rights.
The economic consequences of seeing this policy shift through will result as I’ve said above, in millions or billions of dollars poured into the communications infrastructure of Europe to allow for compliance without relying on U.S. or Chinese server capacity. This means that there will be local economic interests who would be powerfully motivated to support such a shift.
In the larger political climate, the major fact of this decade so far is the decline of U.S. power (please lets not argue about the reasons for that). Russia and China are unlikely to do anything to stop the EU from hampering the reach of the U.S. surveillance structures. Barring some major terrorist attack which creates a massive change in the political climate of the EU, this is going to be an enormously powerful decision.
I think that its not an overstatement to say that the ECJ might have committed the remaining legitimacy of the EU itself to this issue. While its hard to know for sure, I see powerful forces in Europe which will back this move, and I don’t think that it will be the business as usual which the big tech companies are hoping for in their press releases.
One of the interesting features of the BCRs and Model Contracts is that they put the burden of proof on the tech company. That means that simply by accusing Google or Facebook of participating in PRISM, ordinary people in the street can get paid unless the companies can prove that their specific data was never accessed. Once this sinks in there will be hundreds or thousands of cases, as people start wanting their share of the payout.
So while of course Big Tech is making confident statements now (to avoid conceding the issue), they must be running scared.