Just remember that at his start, the game as reached 25 k players pic according steamcharts, far more Warhammer total war is doing now for example.
Many of those players would probably buy a dlc with a new race because precisely they have left the game due to lake of content.
In reality, the number of potential customers is far above because the game have been sold to more than 1 million copies. Anyway, let's concentrate only about those 25k players.
If we suppose that a dlc with a new race cost around 250k (6 devo for 6 months), and this dlc would be sold to 25 k players to a price around 20 euros, then this going very profitable (25 k * 20 = 500 k sales).
In addition, this would boost the game and allow new developpments which would attract more and more players.
Honesty, I don't understand SEGA stragegy. Better to capitalize on a solf already existing and developp it than to abandon it and act loses (which is bad for reputation too).
The guy who cares about strategic marketing and financials underestands nothing to video games and should be fired !