Fox's resident judge Andrew Napolitano has some bad news for Trump: his case for "executive privilege" is likely to lose in court.
There are three big things Trump is trying to prevent:
Mueller testimony: Trump and his White House would love to stop what will be the most-watched testimony of Russiagate Summer, Robert Mueller. They may try to do so if he remains a federal employee but if he's either subpoenaed or ends his work and his employment, there is little Republicans can do to stop the subpoena from being issued and honored.
Redacted items in the Mueller Report: Unless the things redacted relate directly to conversations held between Trump and top advisors (unlikely), there is no executive privilege Trump can claim. A judge can decide to keep the intel from Congress if it is deemed to harm innocents or be against the national interest to release it (also rare).
McGahn testimony: Don McGahn is no longer a government employee, but his conversations held in the White House do fall under the "executive privilege" umbrella. Except Trump gave up that privilege when he let McGahn testify, and there are no "backsies" on releasing testimony. In McGahn's case, the courts would be highly likely to support the Congressional subpoena.