I think the "Void Elf" stuff was planned to appear in 7.3, but they scrapped it. Maybe, originally, Alleria was supposed to have followers that were also using the Void as a tool. The weapons and database entry are just the remains of the idea. Since it never made it to 7.3, they may have continued working on them for 8.0, or they may have given up the idea entirely at this point.