I suppose it's OK for me to spoiler The Hobbit: The Battle of the Five Armies (2014) - They dispatch the dragon right away. At the end of Desolation, we were expecting a very dragon-oriented finale. But Bard (Luke Evans), man of Laketown, puts him down pretty much right away.
The rest of the movie is taken up by the following question: If Bilbo and the dwarves woke the dragon, which attacked Laketown, causing untold destruction, and if Bard managed to kill said dragon at great risk to himself and son, leaving the great horde of gold in the caverns where the dwarves are more or less hiding, then, what the hell, man? Thorin will be the mountain king if he can get his hands on the Arkenstone, a jewel of great power that Bilbo has stolen (to repeat, the hell, man?). He won't share with anyone and is being rather a dick about it.
The men of Laketown are overall quite understanding about this, but reaching their limits. Some elves show up to get theirs back. Some more dwarves show up to help out. Then Gandalf returns to let everyone know: Orcs.
Is someone counting? How many armies is that? Because I'm not going to bother with three or four, but six would be overdoing it, you know?
Ethical dilemma aside, this movie really gives you the promised battle. There are lots of great "marshalling" scenes, with great armies forming up in ranks and taking position. Then, lots of great melees and little one-on-ones. I've heard some complaints that this is a little too video-game, since it's all CGI, but unless those games have gotten a lot better, I think this was a different thing.
I guess this is the last of the Jackson/Tolkein movies. I don't think he'll be doing the Silmarillion or Leaf by Niggle next. At least we have the extended versions, director's cuts, extended director's cuts, etc to look forward to.