Fastjet are still in operation, though they haven't yet made a profit. Fastjet Tanzania have reduced their fleet down to one single A319, and have cancelled a few destinations. Fastjet Zimbabwe recently received a second aircraft, so things seem to be a bit more positive out of Harare.
The management have talked about replacing the A319 with Embraer E-Jets because the Airbus is currently too big for the African low-cost market.
Overall, I think that a fleet change could help reduce costs and may bring the airline into profit, but I'd say that if things don't improve the airline could cease operations by the end of the decade.