The 'Fantastic Five'? Shifty, Pelosi, Joe Biden, Hunter Biden, and the whistle-blower.
Well....I think all will subject the subpoena to the court system, and draw this out for six to eight weeks....meaning that the Impeachment is stalled in the Senate.
If the Supreme Court says they must appear? They will simply say nothing and use their lack of speech to motivate the situation.
McConnell will then say the Impeachment can't move on, and settle it with a end-vote.....no impeachment.
A one-star ending to all the drama? Well....yeah. McConnell will go and say that they could have brought the house down (like the fat lady singing)....if they'd just spoke up.
The public perception of this type of ending? I would suggest that people will sit there for days....admiring how this subpoena was the 'golden goose', and this really turned into a Sugar Bowl game between a number 88-ranked NCAA team and a 104-ranked team.
A drama without drama? More or less.
But here's the one odd thing. Trump can pick up the phone, call the Ukraine on the day after the impeachment is tossed out in the Senate, and do the exact same thing all over again.....this time with forty 'weasels' in the room (maybe even that US Army Lt Col). He might even call Nancy Pelosi over to the White House, and let her listen into the call.