The page does include a population breakdown by sub-species and here is the snippet about the Mountain Gorilla.
Late 1950's: 400 - 500
1973: 275
1981: About 250
1984: 360 - 370
1989: 620
2000: About 600
2002: Approximately 660
2004: At least 700
All of which seems to suggest that the population is at its strongest in 50 years.
