This will be ignored for one or both of the following:
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John Roberts has already signalled his support for the Unitary Executive Theory, which would basically give Trump the power to do exactly what he's doing. Trump will likely immediately appeal this to the Supreme Court, where they will either rule in favor of Trump via the UET, or will simply stall the case for months without issuing a ruling, leaving the affected workers in legal limbo. Those workers still have families to feed and can't wait months for a ruling that is unlikely to even go their way. Most of them will simply move on to other jobs in the interim, rendering the whole thing moot in practice as the end result will be the same: A whole bunch of federal workers losing their jobs.
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Trump will simply ignore the ruling, probably demanding that the judge be impeached and launching a smear campaign against him as well. With no actual enforcement mechanism, the judge's only real response to Trump essentially telling him to go fuck himself is to issue another order "demanding" compliance, which has all the force of law of saying "pretty please". Trump will basically challenge the judge and essentially say "What are you going to do about it?" and that's the last we'll hear about it as the judge isn't going to openly admit that he has no way to force compliance or impose consequences for non-compliance, especially given SCOTUS' previous rulings on Presidential immunity.
Look at it this way. Think of how many other judges have already ordered Trump to reinstate workers. Now look at how many of those workers have actually been reinstated. Look at how many other workers he keeps illegally firing despite those orders. That should tell you all you need to know regarding where this is going to go.