According to the the courts, (In re Du Puy) the delivery of a pardon is an essential component. So if incoming president Biden could block delivery of a pardon, then it could be revoked. That happened when President Grant blocked a last minute pardon by Andrew Johnson, but I don’t think delivery will be an issue here.
It may also be the case that the power of the pardon is suspended while the president is under impeachment. This idea is supported by James Madison speaking to the Virginia Ratifying Convention and discussed in this paper from the Brookings Institution:
The pardon power and original intent
It is conceivable that a court challenge could be made if a pardon was issued against the law, for example a pardon issued for bribery, or perhaps a pardon of the president’s criminal co-conspirator. In that case the crime and criminal conspiracy would be ongoing through the pardon. Those are areas of the law not previously explored by the courts.
I think most would agree that a federal pardon does not preclude a state charge of the same crime if such a state law exists. New York recently enacted legislation to make this principle clear. For example, bank fraud is a both a federal crime and a state crime in some states. Even if a federal conviction were pardoned, the state could prosecute the same crime. Double jeopardy doesn’t apply to state charges and a federal conviction.