وَهُمْ فِي مَشِيئَتِهِ وَحُكْمِهِ
Such sinful believers are subject to Allah’s will and judgment.
One must neither guarantee oneself forgiveness nor assume that every major sinner is doomed. Forgiveness and punishment fall under Allah’s judgment. People are responsible for avoiding sin and repenting, but they do not control the final decisions of the Hereafter.