There are only four deadly strains of Ebola, unless more show up. One would think that yes, a survivor would become immune. However earlier in the thread other people posted examples of other viral diseases that are never really fully treated, just suppressed. A poster above said that he got shingles twice - and it's caused by a virus. As this very article suggests, doctors themselves are not sure if Ebola can reinfect the patient after he is cured. Maybe all that it takes is one flight in an airplane at 30 thousand feet, one highly energetic (gamma) photon that hits the DNA molecule of a dormant virus and messes it up... and now the virus is back in business.
Actually I was talking about the cold viruses.