Once it receives the managers and articles, it doesn't need SCOTUS to find the charges are not an impeachable offesne "as a matter of law" (scare quotes becuse the senate is not deciding a law matter, but an impeachment matter). This precedent would stand until a future Senate reverses it. It would stand both as a valid procedural method, and a valid substantive method.
Totally up to the Senate. It has the sole power in this regard.