One can hardly imagine that Oscar Pistorius found guilty of manslaughter at his criminal trial would be found guilty of murder after the prosecutor appealed. That’s because in the US, the prosecutor cannot appeal a verdict and ask the appellate court to find the defendant guilty of a greater crime.
In our system, a jury decides guilty or not, and an appellate court can set aside a verdict only if there was some legal error or newly discovered evidence and force the prosecutor to try the case again. An appellate court can never set aside the jury’s verdict and find that they would have found the defendant guilty of the greater crime or a crime at all if the jury acquitted him.
For Pistorius, he faces a minimum of 15 years. It appears that the judge has some discretion in sentencing him to a lower sentence, but I do not believe that is likely. Pistorius’s athletic career is over.