What would happen if meningitis went untreated? could someone ultimately get better on their own or would death occur?

Meningitis: Although perhaps not 100% fatal, the percentage is close, and if the patient does not die they may have significant post-infectious neurological and other complications which may be permanent.

Depends on cause: There are several forms of viral meningitis caused by enteroviruses that pass with time and leave little if any long term effects. However, the bacterial forms are more deadly and Even with treatment can lead to death. Treated patients may end up with focal brain damage,seizures or deafness. I have seen several end up in long term care facilities with the life of a vegatable.