The classical definition of the term “Sedevacantist” is one who holds that the Chair of St. Peter has not been occupied since Pope Pius XII.  We now have those who use scare tactics against one who holds Benedict XVI as the true pope by asserting that if Benedict XVI dies before Jorge Bergoglio he becomes a “Sedevacantist”.  Really?  So if Benedict XVI dies before Jorge Bergoglio he comes to hold that the Chair of St. Peter has not been occupied since Pope Pius XII?  Such asserters either don’t realize that they are equivocating the term “Sedevacantist” by giving it two different meanings in the same argument (this is called the logical fallacy of equivocation) or they know they are equivocating the term “Sedevacantist” in the same argument and are hence engaging in sophistry.  In either case, don’t fall for it!  If Pope Benedict XVI does indeed die before Jorge Bergoglio, the Chair of St. Peter ceases to be occupied and a conclave elects the next pope.  Plain and simple.

Pope John Paul II admitted that a Papal Renunciation could be invalid

Pope Benedict’s Renunciation is invalid for 6 Canonical Reasons