Mugabe, 85, took up the party leadership in the 1970s at the height of the guerrilla war against the white-minority government of Zimbabwe, then known as Rhodesia.
He has ruled Zimbabwe since its independence from Britain in 1980 and is hailed by his supporters as a liberation hero.
He has already been endorsed as the Zanu-PF candidate for the next elections slated for 2013, when he will be 89.
But his critics say he is responsible for the last decade of economic collapse and political violence in Zimbabwe and Zanu-PF itself has been divided over who should eventually succeed him.
Joice Mujuru, the vice-president and the wife of a former army general, is seen as the front runner to replace him.
But a second camp is led by Emmerson Mnangagwa, the country's defence minister, who local media have long touted as a possible favourite.
Haru Mutasa, Al Jazeera's correspondent in Harare, said that while there was little likelihood of an immediate split, the division could potentially destabilise the party.
"The fear in people's minds is that if Mugabe shouldn't managed to live out his term - or if he step down for any reason - and he hasn't appointed anyone to take over from him then the factions within Zanu-PF might start squabbling among each other to see who comes out on top," she said.
"The fear is that the groups who want to vie for this position have military backgrounds and could be prepared to do anything to hang on to power."
Despite this, analysts say there is likely to be little overt debate on the subject at the conference.
"There will be no noise during the congress, and there will be no meaningful debate," said Lovemore Madhuku, the chairman of the pro-democracy group National Constitutional Assembly.
Takura Zhangazha, the country director of the Media Institute of Southern Africa, said: "Zanu-PF will come out of the congress still limping ... They won't come out with a pragmatic approach to revitalise the party."
Although the Zanu-PF retains significant support, especially in rural areas, opinion polls suggest that it would probably lose any new election.