Vex Strike Force event is supposed to give the new exotics, no? It's worked that way for me since it came out (I have all but the newest), but today I got a Khepri's Sting instead of the Mothkeeper's.
I did a quick search online, and the last time this happened, a few months ago, they fixed it somewhat quickly, but alas, it's apparently happening again.
Bungie! Please, if nothing else, be consistent! When you fix stuff, it should stay fixed!
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Correct me if I'm wrong, but I don't think that the Vex Strike Force or Lost Sectors have ever been guaranteed to give you new items. They're definitely very heavily weighted to do so, but not 100%.