Eden: No one is allowed to leave Eritrea [without an exit visa] so I’m not sure it will affect the rate of Eritrean travel too greatly, unless one is a member of the "Eritrean elite". With respect to Kenya, I’m sure more privileged Kenyans will be able to take advantage of it.
Jemila: I think other African nationals will visit Ghana - perhaps out of curiosity more than anything else. Ghanaians might be less likely to visit other African countries beyond its West African nations and the usual economic zones (Kenya, South Africa). But ultimately, I think it will depend on things like airline availability, ticket costs, language, basically the practical elements. We might see a surge in Africans in the Diaspora visiting African nations other than their home nation though - think Spring Break in São Tomé (now that I'd like to see!).
Zika: I don't think this AU passport will change anything for the average African because they'll probably never get one - unless it's required and replaces all existing national passports. For those that get one, the high cost of traveling within African will be enough to make it unlikely that the passport will change much. However, I do think this would make the lives of African politicians and business people much easier, which, now that I think of it are the people the AU really represents.