I wonder if Trump's nominated judge will be sitting on the Supreme Court bench when it comes to a decision on this issue. He is apparently on record expressing disquiet about Trump's attitude to judges who disagree. Trump is setting up a grudge match with the Supreme Court judges.
Once the new man is on the Supreme Court bench he is effectively freed of many political and career restraints - and can then follow his own conscience and integrity. I suspect he may not end up as such a hard line conservative as Trump expects.
There are precedents for judges who have reached their final career stage - and would not interpret laws arbitrarily in favour of a head of state decree.
Unless Trump finds a way to blackmail or realistically threaten the judges and their families - then he will find it difficult to just dismiss them.