Yeah, I saw episode 12 like everybody else, and like many people, I was disappointed with the pay off. But after taking a few hours to calm down, I realize it's not THAT bad. It did have some good moments, Issei and Rias kissing (dispite them forgetting afterwards, but it still happened!) I got a few laughs with the Oppai Dragon segment, it makes me want to read the Light Novels allot more and hey, we gots some hints of newer and better stories along the way.
Which brings me to my point. I'm sure that Season 4 is coming, because like I said, there were hints. So I still hope that will get a fourth season of the anime. Fools hope? Maybe. But it's still hope nonetheless. And yeah, as many people pointed out, sometimes shows like DxD take months to about year, maybe 2 years to produce. So hey, if we can wait a couple of years for Season 3, I'm sure a couple of more isn't gonna kill us. And besides, I still think we got a few OVAS coming, not to mention we got all the previous kick ass seasons. So I say let's relax, and have hope that a fourth season will come along and gives us a better finale than before. After all, aren't some good things worth the wait?