I dont know OP .
the favored theories are two .
the first :being Moses and Elijah.. because they were at the transfiguration with the Lord Jesus when he was manifest in his Glory .. and God preformed through them many similar signs as mentioned in revelation.
the
second : being Elijah and Enoch ... i understand the reasoning behind this choice is because it is written that-" it is appointed unto all men, once ,to die .." and these two men both were taken from the earth .. and to all intensive purposes, in our understanding ..did not yet die in the manner we consider to be death .
Enoch was not , for God took him
and Elijah was taken up in a chariot of fire and his body never found.
where as Moses went off and died and though his body was not found .. in Jude it states that Michael the archangel and lucifer contended
for his body ,thus giving the appearance that he did die a natural death already ..
to my understanding this is why there are those two choices...
of course we may all be wrong and James and John the sons of thunder ..might turn up lol ..maybe peter and Paul..even better maybe two unknown beggers who so pleased the lord he sends them ?? . whoever it is it will be two who have
witnessed the lamb of God in All his Glory ..