All I can say is that I hope these lawsuits to block Trump's illegal constructions - Ballroom, Arch - make it to the SCOTUS, and they rule against him, BEFORE he simply begins construction anyway. But will they?

Maybe? I don't know.

The standard for getting a preliminary injunction isn't a slam dunk. And for good reason - you're asking the court to impose a sanction/obligation on the other party even before you or they have made your full arguments. You have to prove irreparable harm (some exceptions not relevant here), some circumstances that make it necessary for the court to step in before it has actually decided who should win.

I'm not sure that's going to be met, here. It's usually pretty easy to meet that standard to prevent something from being destroyed, of course. But the existing building's already been destroyed. Anything new that gets built can be demolished and removed. The government will always retain the ability to return things to the status quo ante if they lose. If the government is willing to take the risk that they might lose and have to remove everything, the courts might simply let them do so.