Nations have clearly been trending larger over history, on average. Unless there's a good reason for this trend to stop after thousands of years, globalization will be the end result. But the process will happen organically, and slowly -- perhaps slower than some would like.
I wouldn't say that is clear at all. Perhaps there is a trend of growing larger before collapsing spectacularly into a bunch of smaller nations, but that is about as far as I would ever be comfortable saying anything is clear on this topic.
Perhaps you're thinking about empires that were primarily held together by military force. Those are inherently unstable. As it pertains to globalization, the more relevant trend over time is the formation of nation states that primarily exist for any other reason.
Your hypothesis is the nationalism that is a recent invention of the last 400 or so years that drives nation states (that we have been trying really hard to destroy in the first world) will cause globalization rather than more of the friction and war it has caused in the past? Nation states only drive unity when there is an other to compete with and by design they can't cause the end game of globalization. At best that process is going to hold an area together through a spectacular collapse, not drive one world unity.
