There’s been a lot of talk about whether a world of many nation states will be replaced by a world of one “nation” state, but not so much about whether the current format will continue. Most of the talk has been about something like what we have now, writ large (only without the military forces, only police forces).
The question was “Will the world always be divided into nation states”. I think the answer is almost certainly no. That doesn’t mean there will necessarily be a single nation-state writ large. I think there probably won’t.
Someone pointed out earlier that the nation state is a modern (literally in terms of historical epochs) historically specific invention. The current international system (or the one that is coming to an end if you believe we are in a time of major change) is generally held to date from the Treaty of Westphalia in 1648, which ended the 30 Years War and 80 Years War - although there are of course revisionists and dissenters. Regardless of the significance of Westphalia to our current international system, systems come and go and our current one will come to an end too - it would be supremely arrogant to think differently. The only question is how will it evolve or what will replace it.
One of the significant properties of the modern nation state is its supposed monopoly on the legitimate use of force. Ok, you could say that parents have a legitimate right to use force on their children (send/take them to bed) or you have a legitimate right to throw a burglar out of your house, but within the terms of the system, these are essentially rights granted by the state and legislation can change that.
Prior to Westphalia, nations existed. But they weren’t sovereign nation states. In England’s case, that’s why Henry VIII had to tell the pope to fuck off so he could form the Church of England with him as its supreme head. A precursor to what was formalised and systematised later. Before the Reformation, though England existed with a legislature, King, borders and an army (though not a standing army I think), it didn’t have supreme sovereignty. The king was part of a feudal chain of command ending in the Pope.
For a while, sovereign states existed with supreme authority within their own borders and waging war when they didn’t like what was going on beyond those borders. Although they’ve never been the only ones to use force, they’ve claimed to be the only ones to legitimately use force - Bin Laden’s army is supposedly illegitimate, Bush’s army is supposedly legitimate.
Can we really say that’s true post WWII? There are loads of international institutions that constrain nation states, world wide - UN, WTO, IMF, WB etc and many regional ones - EU, AU, ASEAN etc. Not all nations are members of all these organisations, and those that are have joined by choice - but at this point it would be very difficult to uninvent them or the treaties that created them. Bush himself struck a blow for the decline of the nation state (aside from the decline of The US by fighting a war too far) by asserting his right to intervene in another sovereign state. According to the premises of the war, Iraq clearly didn’t have the right to do what it wanted within its own borders.
So the question is what will replace the current international system, which is already evolving. I think increasing numbers of parallel global institutions as well as regional and local ones, ultimately creating a global system is likely. The global institutions are unlikely to have the universal power over the people of the world that nation states did at their height (education, health, crime, punishment, social security, birth, marriage, death etc) and there will still be conflicts, probably ones involving force - it’s just it won’t be classical nation states fighting them. Which brings us to Al Qaeda and The War Against Terror.