Is it possible for goku to achieve a level higher then the ultimate super saiyan 4

It wuold probably be possible to reach a higher level than Super Saiyan 4, but he would need to train more and have more rage. But this will not happen since Akira Toriyama finished creating Dragon Ball GT. Dragon Ball AF is non-sense and the pictures are inaccurate. Even though AF shows Goku in Super Saiyan 5 form, it is a fake picture.