Ethics has been consistently appearing as two item sets in the PM paper for CFA Level III since 2012. However, as @artyeasel says this is not to say that this is not to say that it won’t happen in the future.
It’s always in the item-set section as far as I know. I’m not sure if that’s a guarantee of future exams though – the essay format could easily lend itself to ethics (and make it a lot more difficult)…