They have been saying this for decades, Cameroon at 1990's (when they beat Maradona's argentina in opening game) Nigeria mid 90's, Ivory coast with Drogba in the 00's.
I don't think it will happen in the near future, South-American and European top teams are way to professional, consistent and organised for any african country to make a serious swing for a final spot. There have been lots of "surprise semi finalists" in WC history, but at that stage you inadvertently meet the real contenders which are "in form" from the traditional strong countries.
Senegal 2002 was also pretty amazing and could have achieved greater things with a wee bit more luck against Turkey in the round of 8.
The real trouble of Africa is the lack of continuity. Every four years you see different teams rising up, but you see never teams who have already been good improving on their foundation and building up an ever stronger generations. The African teams just swing up and down like a yo-yo without ever raising the median.
Local corruption will never let football develop a good foundation or continuity in African countries.
Altough some african teams have been impressive I still think they have no chance against any of the top 4 "in form" traditional teams on a WC. They are bound to meet those before the final and you can be lucky once (like South Korea vs Italy) but it mostly dies soon after.
There are some decent African teams, but the really good ones have been flukes, like Ivory Coast. Sometimes you just get a golden period in a country out of nowhere. I do think that Africa will start producing better teams though, having the world cup in SA will have sparked more interest in football.
Popularity of Football has always been high in the whole of Africa, 2010 WC didnt change that much towards that imo.
The corruption fucks up any kind of continuity or building a good infrastructure for sports in these countries. Member in these countries the local FA stooges are just in it for themselves, without any real critical feedback from population. They will not invest in their league, continuity, vision, long term strategy or youth academies if they can slosh that money towards themselves.
I favoured Uruguay after having seen how amazingly they played in the first games. It was very exciting to see such a classic team make such a revival.
I would have been happy for the Africans if they had managed to reach the semis for the first time, but Ghana (or any other team) definitively wasn't in the shape for that.
I supported Ghana in the 2010 wc. So disappointing when they went out, but I think it just goes to show that an African win is not far off now.