I would say there is near a zero percent chance the Supreme Court would hear any case brought due to this Impeachment. They have a pretty long history of not ‘looking past the doors’ of Congress. That’s the colloquialism that essentially means the Court won’t interfere in how Congress makes their own sausage.
If Trump were convicted - he won’t be - then there’s a slightly better chance that they would entertain a challenge to the question: Can a former president be convicted of Impeachment? That would perhaps be answered due to the ballot access ramifications.
But, if the Dems want to have months of prosecution witnesses while disallowing defense witnesses, the Court isn’t going to weigh in.
They might hear it strictly on the basis of the Constitutionality of the Impeachment of a former Pres, now private citizen, but limit it to that legal point.