A subpena for what exactly? The moribund muh Russia investigation?
I read this as Fake Media raising on a busted flush. If they push Trump to testify, that will be a big mistake.
For [them]. POTUS has it all. That includes the evidence. The public evidence. Not just the stuff on the server[S].
This is just Trump negotiating from a position of strength. And [they] know it, even if the normies don't.