According to Annette and Bill Moon's blog about their senior mission to the Democratic Republic of the Congo, a new stake will be organized this Sunday in the capital city of Kinshasa. Membership in the DR of Congo is close to 20,000 and there is also very high activity (the Mission President reported attendence at district conferences in the interior of the country to be around 80%). This will bring the number of stakes in Kinshasa to four, which makes this city tied with Accra, Ghana for second for the most stakes in one metropolitan city in Africa (the most being Johannesburg, South Africa).
There are around 100 missionaries serving in the DR of Congo Kinshasa Mission. Native languages of the peoples in the DR of Congo where missionaries currently serve are Lingala (Kinshasa area), Swahili (Southern part of the country) and Tshiluba (central region of the country). After this stake will be organized, there will be five stakes in the DR of Congo. The largest stake, the Lubumbashi Stake with 15 wards, has not been split yet from what I know.