First off all, you can't "become" a Naaru. Becoming a being of "Pure Light" doesn't mean is a Naaru. Naaru are beyond ancient and their cycle of Light and Shadow is established lore. Shaohao's "ascension" seems to be taken from Buddhism and the concept of ascending to Nirvana, an ultimate state of being, which fits the Asian theme quite well. And as for Blizzard having Velen dropping meaningless hints, yes, they do this frequently. Fan speculation runs rampant and a whole lot of "facts" are thrown around the forums without any official Blizzard sources.
As it stands:
Elune is a Goddess, matron of the Night Elves and Ancients, associated with one Moon of Azeroth.
Shaohao was a mortal whom, in his quest to purge himself of negative emotion "created" and then imprisoned the Sha with the help of the August Celestials.
August Celestials are Pandaren analogs of Ancients/Loa representing powerful magical forces associated with positive emotions.
Naaru are beings of Light and Shadow with a complicated cycle based on bring life and sowing death.