That's not what the 20th amendment provides. The 25th only applies to when a President dies, resigns, or is removed, not before the person becomes President.
Seems like Biden would become president one amendment or another and a "Constitutional Crisis" will be avoided. It would be fascinating to see it played out. If not for the entertainment value seeing the Libtards whine and spew over 0zero getting caught being the liar that he is.