I heard an interesting podcast episode recently, The Prophet Elijah Will Arrive BEFORE the Day of the Lord, that mentioned a couple things that resonated. He covers:
1 Jesus envisioned his ministry in two phases, his first and second coming.
2 Gabriel's statement about John the Baptist indicates that he was not the intended fulfillment of Elijah's coming.
3 John the Baptist himself explicitly stated that he is not Elijah.
4 Elijah may be one of the two witnesses, who will arrive in the future.
5 Elijah never experienced death, which may suggest a future coming.
6 The conjunction of Elijah and the Transfiguration, which was a preview of Jesus' second coming, connects Elijah with Christ's second coming.
Below is not entirely what was discussed, but some of the points in my own words with some additional thoughts.
Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the LORD: And he shall turn the heart of the fathers to the children, and the heart of the children to their fathers, lest I come and smite the earth with a curse.
This clearly seems to tie Elijah before the day of the Lord. But wasn't John the Baptist Elijah?
And from the days of John the Baptist until now the kingdom of heaven suffereth violence, and the violent take it by force. For all the prophets and the law prophesied until John. And if ye will receive [it], this is Elias, which was for to come. He that hath ears to hear, let him hear.
But the angel said unto him, Fear not, Zacharias: for thy prayer is heard; and thy wife Elisabeth shall bear thee a son, and thou shalt call his name John. And thou shalt have joy and gladness; and many shall rejoice at his birth. For he shall be great in the sight of the Lord, and shall drink neither wine nor strong drink; and he shall be filled with the Holy Ghost, even from his mother's womb. And many of the children of Israel shall he turn to the Lord their God. And he shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord.
It's one thing to come in the spirit of Elijah and another to be Elijah. If you do a word study on the day of the Lord, this was clearly not at Christ's first coming, but it will be tied to His second. I do believe we have evidence from the two witnesses that would imply one being Elijah.
My personal thought is that the two witnesses will arrive sometime in the first half of the 70th week, probably around the time of the temple dedication speaking the truth about Christ and providing a warning, the Gospel, to love God and each other, the truth basically. 1260 days later they will be killed in Jerusalem, which is why I think their arrival will be God speaking truth through them so they are without excuse who choose the antichrist.
Interestingly, I think it's possible that the dragon's false prophet may claim to be Elijah and if Christ's second coming is the fulfillment of the fall feasts like His first was the fulfillment of the spring, the 70th week of Daniel would begin during Unleavened Bread 3.5 years before. Jewish tradition leaves a place setting empty for Elijah to come at this time of year. How appropriate would it be for the false prophet to arrive and prepare the way for the false christ at the beginning of the week when tradition, not scripture, expects it? That along with many of the signs and wonders might deceive many Jews into believing it is Elijah, coming when they expect, and pointing to a leader who is making the temple possible again, defeating their enemies, and seeming to fulfill certain prophecies that can be read several ways.
And after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart, And was transfigured before them: and his face did shine as the sun, and his raiment was white as the light. And, behold, there appeared unto them Moses and Elias talking with him.
It seems clear that both Moses and Elijah have some participation in God's plan. I believe it may be that John came in the spirit of Elijah preparing the way for the True Messiah, but the actual Elijah will come with Moses perhaps to stand before Israel in Truth and power. So the true Elijah will be paired with another, likely Moses, performing the same miracles they were known for from history.
I believe the false prophet may appear to come in the spirit of Elijah by himself, a kind of false John the Baptist, seeming to have some of the power of Elijah to deceive Israel.
And I beheld another beast coming up out of the earth; and he had two horns like a lamb, and he spake as a dragon. And he exerciseth all the power of the first beast before him (spacial, not temporal), and causeth the earth and them which dwell therein to worship the first beast, whose deadly wound was healed. And he doeth great wonders, so that he maketh fire come down from heaven on the earth in the sight of men, And deceiveth them that dwell on the earth by [the means of] those miracles which he had power to do in the sight of the beast; saying to them that dwell on the earth, that they should make an image to the beast, which had the wound by a sword, and did live.
Given that Elijah also brought several people back to life, God may use this as the great delusion when the deadly wound is healed, seeming to have been accomplished by the false Elijah, yet truly by God so that those who wanted to believe the lie would.
It seems fitting for Satan to use deception to effectively break off the natural branches from the root, cutting them off from God, and then using the fervent following of the letter of the Law and misinterpretations of prophecies to turn the unfaithful Israel against the faithful, families turning on each other for believing or not that Messiah has come and ultimately leading to those that choose to follow and obey the antichrist killing their own people at his command. If they truly believe he is the messiah, would they not do whatever he says, even if it goes against the spirit of the Law, love God and love your neighbor as yourself?
Does the dragon want to kill all God's people? Of course, but once they are loyal to him, he has already killed them eternally through his deception. Now they are his tools to accomplish his goal of wiping out all those who do not worship him and create his kingdom with the short time he has.
That's one possibility anyway as I see it, time will tell as we get closer.