"Although I don't necessarily think it will be because of war, I can see a potential future where people/persons decide democracy is a less effective system"
Its probably worth pointing out just how unlikely it is that it would be because of war. The democratic peace is probably the closest thing to a universal law of international relations that we have. So if democracy does have drawbacks in terms of speed of decision making, it has more than its share of upside too.
Eh. The democratic peace theory really just relies on a perpetual no-true-Scotsman approach. Either something's not really a democracy or not really a war.
Native American tribes? Well, they had democratic societies, but they're very different from the liberal state that has come to predominate in contemporary times. Franco-Prussian conflict? Prussia's legislatures were dominated by a rich hereditary landowning class. American Civil War? Well, civil wars don't count, and the franchise wasn't universal. World War I? Well, Germany might have had elections and might have had a wider effective franchise than many parts of the USA, but it was a bad guy, so it doesn't count. Various conflicts fostered by the Western liberal democracies (Iran, Chile, etc.)? Well, those were coups and not really wars.
What "democratic peace" really seems to mean is "countries that are under the umbrella of the United States and have highly developed economies don't go to war against each other." Give it 20 years time, and when the newly elected government of China gets into a shooting war with the government of the United States over some stupid shit (poll driven aggression in the strait?) we'll go back to arguing that China isn't a real democracy because it had only had one or two national elections, or the United States isn't a real democracy because all its state apparatus and elections are controlled by an unelected elite.
countries that are under the umbrella of the United States and have highly developed economies don't go to war against each other
Except in the case of the Falklands War. And the Israeli bombing of the Iraqi nuclear reactor (Iraq was a US ally at the time). And the Turkish/Greek air battles over the Aegean Sea (eg, Turkish & Greek F-16's dogfighting and crashing into each other in 2006: http://en.wikipedia.org/wiki/Greek%E2%80%93Turkish_relations...).
The early Romans had some good success with temporary emergency dictatorships to cut through the deadlock in times of emergency. This didn't really stop working for them till they faced the threat of Hannibal, and appointed Fabius Maximus who spent a few years studiously avoiding direct conflict with Hannibal, and the Senate got impatient and wrested back control.
Its probably worth pointing out just how unlikely it is that it would be because of war. The democratic peace is probably the closest thing to a universal law of international relations that we have. So if democracy does have drawbacks in terms of speed of decision making, it has more than its share of upside too.