Does theonomy require commitment to a particular view of eschatology (end times)?
The quick answer is no. There are a variety of approaches to theonomy, just as there are a variety of approaches to eschatology. The most pessimistic, near-futurist, "Jesus is coming back tomorrow, because I've calculated it from the hidden codes in scripture" person can (and should) still preach today that God's law is good and must be our standard for ethics and government.
Eschatology is contentious
Eschatology can be a contentious issue. One (futile) way to avoid contention is to suppress discussion of alternative ideas. Certain churches and Christian teachers avoid teaching anything other than one particular view of eschatology. They believe they know exactly what the book of Revelation means. No other interpretations are necessary (or even possible). I grew up in a few of these churches. Premillennial, pre-tribulational dispensationalism was the only possible view.
Now, it might be true that one of the forms of premillennialism is the correct interpretation of Revelation 20. But it also might not be true. If you are a Christian teacher, you are teaching falsehoods if you claim that premillennialism the only possible way to interpret that passage. And if you don't even mention the other views, then you are not being a good teacher. If your view is correct, then you have nothing to fear from teaching that reasonable Christians can differ on eschatology.
Postmillennialism not required
Postmillennialism has often been associated with theonomy. Many of the more vocal modern proponents of versions of theonomy also subscribed to postmillennial eschatology. The broader "Christian Reconstruction" movement (begun by people such as Rousas Rushdoony and Greg Bahnsen) associated several different concepts together, which they believed were complementary to their broader scriptural understanding. Postmillennialism and theonomy were two of these concepts.
But Greg Bahnsen wrote:
The thesis of theonomic ethics is not logically tied to any particular school of millennial eschatology. ... Critics trip themselves up by confusing the question of what ought to take place in the world (ethics) with the question of what will in fact take place in the world (eschatology).
This is not to say that one's eschatology does not affect how one views the law. People have used eschatological conclusions to deny the relevance of God's law in many ways. But these conclusions are often a result of more basic theological mistakes (such as the conflation of law and covenant), than a logically necessary conclusion from premillennialism or amillennialism. Faulty theological presuppositions can work their way into any eschatological system.
Here are two critical facts which all Christians should believe, regardless of their eschatology:
- Jesus is reigning as King right now.
- Jesus' (YHWH's) law teaches us how to love Him and love our neighbor.
There are ways in which a faulty eschatology (e.g. certain forms of pre-millenial futurism, certain interpretations of Matt. 5:17-19) could hinder someone from believing the above two facts.
Dispensationalism is an easy target here, and it has come under fire from a lot of theonomists (with good reason). But even committed dispensationalists could (and should) support theonomic ethics. They can do this without giving up any of their important presuppositions (such as the church/Israel distinction).
One of the main reasons YHWH gave the law to Israel was for them to be an ideal example "to the nations/gentiles":
5 Behold, I have taught you statutes and ordinances, even as YHWH my God commanded me, that you should do so in the middle of the land where you go in to possess it. 6 Keep therefore and do them; for this is your wisdom and your understanding in the sight of the peoples who shall hear all these statutes and say, “Surely this great nation is a wise and understanding people.” 7 For what great nation is there that has a god so near to them as YHWH our God is whenever we call on him? 8 What great nation is there that has statutes and ordinances so righteous as all this law which I set before you today? Deuteronomy 4:5-8WEB
The implied answer to Moses' questions is: No other nation. No other nation has statutes and ordinances so just as the laws given at Sinai and after. YHWH intended these laws (the ones which weren't covenantally-bound) to be followed by the nations/Gentiles who observed and interacted with his people.
YHWH put certain cultural protections into his law, to act as a hedge against synchretism. But he did not isolate his people from the surrounding nations. He commanded his people to care for foreigners (Lev. 19:33-34, Deut. 14:21), protect runaway slaves (Deut. 23:15), and provide justice to foreign refugees (Num. 35:15, Exod. 12:49).
YHWH cared (and cares) just as much about injustice happening outside the boundaries of Israel as injustice within. He gave his good laws to deal properly -- justly -- with acts of injustice. He gave his laws as a transcendent standard to define crime and "evildoing", and also to limit the scope of civil government (Deut. 4:2). He subordinated human rulers to his unchangeable law, so that they would not lift themselves up above their brothers (Deut. 17:18-20).
- Bahnsen, No Other Standard, 51-52