Actually, it's official when the deals are signed - we then find out about it when the studio or production or actors' reps make it public. Being reported at startrek.com has nothing to do with making it "official" and they often lag behind many other news organizations in reporting on Star Trek - notably the trades like Variety and Hollywood Reporter and often fan-run sites like www.trekmovie.com.
In this particular case, trekmovie.com and even startrek.com are out ahead of the trades.
In this particular case, trekmovie.com and even startrek.com are out ahead of the trades.