People like to speculate, and with a system like allied races in place, people will try to predict what we are going to get next.
As for the OP…
Actually, it is a good indicator, for the simple fact that Blizzard won’t spend a ton of resources for something it has no plan to use. Making playable-quality models for NPCs is a waste of resources unless you have more plans for them than being featured in a single zone and forgotten later.
There has been NPC models capable of using gear since the beginning. Old goblin models, TBC ogre models, forest troll models, male vrykul, TBC broken, TBC naga… But they are clearly NPC models still: their customization is very limited, they can’t equip every slot, their animations are very crude, there are some glaring clip problems, the textures are of lower quality…
This is nothing compared to the amount of work Blizzard did on vulpera and junker gnomes. Both have models fit for players: HD textures, high polygon count, several customization categories, able to equip most gear, new animations. Neither are finished so far, but neither were Zandalari and Kul Tirans before 7.2.5, when they got their last few touches.
“Follow the money”. If Blizzard is spending too much resources on these models, you can guess with a higher chance of success that they’ll end up playable.
Why would there be 7.2.5 content in 7.2 PTR?
And vulpera and mechagnomes ARE in 7.2 PTR anyway: they are in the races tab files; their models are there for everyone to see.
Blizzard will of course announce allied races in advance, but that does not mean they aren’t working on those races right now. We know almost nothing of future patches (the only post-8.2 feature we know of are the new goblin and worgen models). No one can say with certainty if 8.2.5 will have allied races, but even if it doesn’t, that does not rule out 8.3 or 8.3.5.
But we do know Blizzard is working on more allied races, so it’s reasonable to speculate on that front.