I wonder how many attempts it will take for this deal to be considered legal before the US actually has to do something to hold up their end of the deal. The US government would scream in rage if Germany would ever demand the ability to order Microsoft or Google to hand over information about US citizens in complete secret, yet the EU wil gladly take the word of the US government that it won't happen.
The EU also has plenty of incentive to encourage keeping data within the boundaries of its member states. Making it difficult to use American tech giants as a lazy quick fix for data storage instead of looking at local alternatives only helps limit the amount of money taken from the European economy. With the scandals and state of the current US government I find it hard to believe the EU will be able to draft a new agreement like this with the US without compromising on the rights of their citizens.