I believe eventually all four of these empires will be absorbed, maybe perhaps by the EU or future little horn. Its possible the four phased statue is the same as these four horns from Zechariah. Reading from Daniel 2 it does sound like all four parts of Daniels statue are destroyed at the same time.  Zechariah 1 even says they will and

 

Jeremiah 30:7 Alas! for that day [is] great, so that none [is] like it: it [is] even the time of Jacob's trouble; but he shall be saved out of it.

Jeremiah 30:11   For I [am] with thee, saith the LORD, to save thee: though I make a full end of all nations whither I have scattered thee, yet will I not make a full end of thee: but I will correct thee in measure, and will not leave thee altogether unpunished.  

 

 Daniel 2:35   Then was the iron, the clay, the brass, the silver, and the gold, broken to pieces together,     and the wind carried them away, that no place was found for them: and the stone that smote the image became a great mountain, and filled the whole earth.   

 

Zechariah night vision # 2

Zechariah 1:21 These [are] the horns which have scattered Judah, so that no man did lift up his head: but these( Four carpenters) are come to fray them, to cast out the horns of the Gentiles, which lifted up [their] horn over the land of Judah to scatter it.

 

The four Phase Statue 

 

1. Babylon

2. Media- Persia

3. Greece

4. Rome

 

FOUR HORNS OF ZECHARIAH 1 (F&B)

 The Spirit in the prophet looked farther; namely, to the four world powers, the only ones which were, or are, to rise till the kingdom of Messiah, the fifth, overthrows and absorbs all others in its universal dominion. Babylon and Medo-Persia alone had as yet risen, but soon Graeco-Macedonia was to succeed (as Zec 9:13 foretells), and Rome the fourth and last, was to follow ( Dan 2:1-49 7:1-28 ). The fact that the repairing of the evils caused to Judah and Israel by all four kingdoms is spoken of here, proves that the exhaustive fulfilment is yet future, and only the earnest of it given in the overthrow of the two world powers which up to Zechariah's time had "scattered" Judah ( Jer 51:2 Eze 5:10, 12 ). That only two of the four had as yet risen, is an argument having no weight with us, as we believe God's Spirit in the prophets regards the future as present; we therefore are not to be led by Rationalists who on such grounds deny the reference here and in Zec 6:1 to the four world kingdoms.