I see it more as Assange distancing himself so that nobody later says he outed a WL source in case the allegations turn out true. If anything, the Nieuwsuur interview in August was more of a wink wink but still hardly qualifies as evidence.
Yes, hardly, because there is little chance that Assange is going to confirm this.
We don't even know for sure if he actually knows something or simply pushes for investigation of this murder solely because other leakers are worried that this conspiracy may possibly be real and that the same could happen to them.
Or because his room in the Ecuadorian embassy is too small and he would prefer to live in Moscow with Snowden /s