Yeah, I've played the hell out of Civ IV and Civ V, so I've experienced the endgame a lot.

And actually, to add to my previous post, there are two ways it has always ended for me.

You and the AI manage to end up equal in troops, and sit there throwing troops away against equal troops of other nations in a nonstop battle of attrition. Brings to mind thoughts of the never ending human meatshields of Russia on the eastern front in World War II. It just slows down and you sit there trading bits of land here and there, forced to throw away entire armies or nuke people just to gain the edge. Most times, the only way to win at that point of a game is actually nuking people. Nuke the hell out of them to gain an edge and let it carry you to a win.

Then there's the second way it has ended for me, and that is I end up jumping out to a large lead over the AI in research and military, thus I can always keep the edge on them through the length of the entire game, so when I reach the endgame, I have armies that are superior by at least a research/advancement generation or two, and have troops by the hundreds of units, as opposed to AI nations that have maybe a couple dozen cavalry to go up against my tanks. So when I hit the endgame, it's just one giant rape-fest as I steamroll every AI in the game on my way to a victory. And generally I can only play with conquest/domination as the method of victory because Science, Technology, Diplomacy and the other ways of victory end up being too easy to achieve and too simple to beat the AI with.

So I'm definitely hoping the additions that are coming in Brave New World will help to expand on the endgame and lead to a better game during that time, help keep it more interesting and make it more complex instead of either steamrolling the AIs or nuking them all to hell to stop the never ending wars of attrition and win the game.