This could not happen to avoid impeachment (The Democratic Speaker of the House said he wanted the VP position filled before continuing for Impeachment so that it didn't come off as a coup to Republicans following Spiro Agnew's resignation from the position).
That said, the VP can become Acting-President for a time where the POTUS is not able to perform his duties but will return at a later time (George H.W. Bush duringafter the attempted assassination of Ronald Regan as well as Dick Cheney during surgeries that George W. Bush underwent.). Upon return to health, POTUS resumed duties and the Acting-President was demoted to VP.