We have done extensive research, and spoken to many artists about forums. Based on feedback from artists, we have decided that we will not be adding forums to ArtStation.
We may change our mind in the future, but for now there are no plans to add forums. It doesn't fit in with the product vision as a professional portfolio platform. The majority of artists we speak with want ArtStation to be focused on the art, and less about the drama and noise that forums bring.