I think the US would have withdrawn from Somali within a year or so at the most even without the incident. The local population was irrationally, and in some quarters fanatically opposed to the UN mission, even though they were only there to deliver food, and only started fighting when warlords like Aidid attacked them. Aidid and other warlords would have continued attacking the UN forces, inflicting casualties on the less well-trained contingents.
Although even without the "Black Hawk Down" incident, there is a pretty good chance that the militiamen would have started shooting down US and UN helicopters. According to Bowden's book the Somalis and some of their Islamist allies had created time detonators for their RPGs.
Boutros Boutros-Ghali might last for a second term at the UN, since it was the Somali debacle that first started to strain his relationship with the US (though Rwanda and Yugoslavia did not help his case either). A two term Boutros Boutros-Ghali UN Seccretaryship means no Kofi Annan as UN Secretary.