I am against world government on precautionary grounds – we simply do not know what its actual results would be. We may hope that if we get a world government it will be a good one, but we must expect that it could be a tyranny. Only a minority of currently existing governments are competent, low in corruption, accountable, and constitutional. A world government would be more likely to reflect the inadequacies of the majority of governments.
But, how likely is a world government?
First, it is not necessary. The classic argument for world government is that it is needed to secure world peace, to stop us destroying ourselves. But this is no longer relevant. The world has entered a period in declining war. If world government is not necessary for world peace, then its chances are much diminished.
Second, there is no real trend towards more centralized power on a the world scale. The United Nations is not steadily accumulating more power.
So, world government is not on the horizon. Now, I admit that may be wishful thinking on my part, but I think it is solidly based.