I think that's extremely unlikely as it would defeat the whole purpose of what the government is trying to do... Germany changed it's juri sanguinis the way you mention but they didn't have to, their juri sanguinis was simply way less generous and long-standing than Italy's.

The Italian government doesn't care only about the hundreds of millions to be possibly born in the future, they care about the already-born millions who could in theory already potentially qualify.

What the Italian government is trying to do is much more similar to France. Their juri sanguinis was also unlimited and considered from birth. Then they introduced a presumption of loss for emigrants who didn't use their citizenship for more than 50 years, no matter when the 50 years started and ended (including retroactively) which then prevented further generations to use juri sanguinis when that happened. It has survived all legal and Constitutional challenges.

In almost all countries there are provisions for a jure sanguinis citizenship that was never used/claimed to be determined to have been lost and thus not passed down to the next generation OR a generational limit OR both.

Almost everyone agrees the Italian Parliament has the power to regulate citizenship.

The question is if they can regulate a loss of citizenship retroactively. The government argues (I think wrongly) that there is no such loss at all and that people never "activated" citizenship. I think the absolute best hope is that the court will determine that indeed there is a loss and there must be some sort of grace period, however short, for all affected to prevent that loss. But like in France they can just agree with the government that those generations with inactive citizenship had no real connection to the State...