There is nothing new about people threatening our interpreters: all baddies figure out pretty quickly how much we depend on them. In Croatia, I had a young Serb female interpreter. She worked under a considerable amount of stress: local Serb a**holes regularly threatened her as a "traitor" (especially once we started weapons confiscation, etc), and the Croats had a standing threat that they would arrest any UN Serb interpreters who came on their side of the line.
IMHO it isn't realistic to think that we can train all our troops, every six months, to speak whatever the dominant language/dialect of the operational area of the day happens to be. Where we are engaged long term, as we seem to be in Afgh, it might be reasonable to try to establish a survival capability throughout the Army, but realistically it is up to an individual to learn a language, and they have to practice it regularly or it fades away. I think we'll always depend on interpreters, who also bring important local and cultural understandings that we just will never have, unless we live in the region for years.
Cheers