The government could ram it through when there were no court objections quite yet but with them the dissenting voices inside government certainly get amplified. Also, while violating the constitution has been quite a sport for the government in Germany in recent years, court decisions that ruled laws unconstitutional have been respected.
I’m quite optimistic, but there obviously remains a danger of this being implemented some years down the line.
I have no idea what this means on the European level and for other individual countries, though.
When it comes to security, don't live in hope that the bad actors (in this case, governments) won't do what's possible because of something that's fungible (law).
Also, while secret services may do all kinds of bullshit hidden in the dark something like the data retention law is out in the open and consequently comparably much easier to contain. It’s possible to have a proper discussion about it. (I think this also quite neatly illustrates the value of having those discussions out in the open, both when it comes to the courts that decide on it and to the political pressures. If it happens in secret it is much, much harder to control and contain. Policy that is decided on in secret – even if by elected representatives or people appointed by elected representatives – is just much more dangerous.)
Will the average ISP pay to put all its staff who have acess to those records with access through TS (DV clearance) clearance its not cheap. And what happens when some of the staff fail vetting - oops your now out of a job.
Oh and this woudl mean that ISP's would have to have judicial oversight.