No, he will only be half-demon in the end. Becoming a great youkai will make you lose your true nature, and after meeting Kagome, he realized that being a half-demon was not bad, as he had the power to protect Kagome and the tenderness of humanity. Becoming a real monster requires the power of the Shikon Tama, but the ending tells us that the Shikon Tama will not really fulfill people's wishes. It is an evil thing. After being destroyed by Kagome, it lost the channel to become a big monster.