There is a risk to stopping Wellbutrin abruptly. You could have seizures. If you want to stop it, it would be best to taper it over a at least a few days to a week. Most of the time you are better of tapering off medication. As far as stopping the Abilify, there is definitely a risk that the voices will come back.
I don't know your diagnosis, but my guess is that it is Bipolar with psychotic features or schizoaffective. Both of these illnesses have a high rate of exacerbations without maintenance medications. The trouble with that is that subsequent episodes tend to be more severe and harder to treat and you do not always return to baseline functioning.
Please see your doctor and talk to him about your desire to reduce the amount of medications. Only he knows your history and the risks involved. If you are not happy with your doctor, seek a second opinion.
I'm a psychiatric nurse