Silvermoon-EU yes .I play on Bleeding Hollow, which is usually a high-pop realm around the clock. I've seen that its dipped down to medium on the login screen, and can generally tell that there are fewer players hanging around the populated areas. But no, its not dead.
Some of my alt servers however, feel quite underwhelming in terms of population. I'm not sure if the posters above me are discussing Silvermoon-EU, but from my experience Silvermoon-US feels really sparse..