Someone tweeted that the fourth one might be Ely Buendia. We'll see then!
With this confirmation from Lea Salonga, it means she is the Voice that Conquer the World as mentioned in the teaser that was released by ABS-CBN early this week.
It's official: I am a coach on THE VOICE OF THE PHILIPPINES! I wonder who coach #4 will be. @thevoiceph
— Lea Salonga (@MsLeaSalonga) February 19, 2013