I am sorry to learn of your wife's malady right now - and hope that she will seek (and accept) appropriate treatment to address her mental health needs.
Bipolar Disorder and Schizophrenia are two different disorders and rarely co-occur. A third disorder, Schizoaffective Disorder, may also explain some of your wife's behavior - but this is not a diagnosis, by any means. (It is inappropriate and unethical to diagnose via the internet.)
Bipolar Disorder, Schizophrenia, and Schizoaffective Disorder are all considered chronic mental health conditions. The origins of the disorders are unknown, but it is felt to be a brain-based disorder. While there is no "cure" for these disorders, there are very effective treatments for managing the symptoms. Some individuals with these disorders are able to lead happy and productive lives - provided they continue to seek and accept appropriate treatment.
It is unlikely that your wife's condition will IMPROVE without treatment. At best, XXXXX XXXXX "level off" and remain in her current state for some time. It is more likely that her condition may worsen without treatment - but there truly is no predicting how each individual will manifest the behaviors associated with each disorder. In short, diagnosis and prognosis are two "no-nos" over the internet.
Finally, regarding the likelihood of permanent custody, I assume you currently have permanent custody of your children since you are their father. Unless you have lost custody for one reason or another, there would be no reason why you would lose it now. The larger question is whether or not your wife will lose custody due to incompetence or presenting a danger to self/others. This would require consultation with a lawyer, who will likely want further consultation with a Licensed Mental Health Professional (Psychiatrist or Psychologist).
I wish the best to you and your family. I hope this was helpful.