In the version I read, it says, "On all this Bilbo looked with misery. He had taken his stand on Ravenhill among the elves – partly because there was more chance of escape from that point, and partly (with the more Tookish part of his mind) because if he was going to be in a last desperate stand, he preferred, on the whole, to defend the Elvenking." (Chapter 17 - the Clouds Burst, page 286)
Now, I may be misinterpreting that passage, but the way I read it is that Thranduil is 1. still thoroughly involved in the fight, and 2. on Ravenhill.
(I wrote an essay on the Elvenking way back in 2003-ish when he was being slandered in fanfic -- slander which is of course now nearly movie-canon, but if anyone is interested, the essay can be found: http://tree-n-leaf.livejournal.com/ or https://www.fanfiction.net/s/10780933/1/In-Defense-of-the-Elvenking)
*sigh* I'm not sure I've ever been so excited about a movie that I so simultaneously dreaded.
