Michio Kaku, a renowned theoretical physicist, has expressed optimism about the potential discovery of a theory of everything, but he has not made a specific prediction that it will be found by the year 2100. It is important to note that scientific predictions about specific timelines for major discoveries are inherently uncertain.
String theory is one of the leading candidates for a theory of everything, as it seeks to explain the fundamental nature of all particles and forces by postulating that everything is composed of tiny, vibrating strings. However, it is still a highly speculative and mathematically complex framework that has not yet been definitively proven or verified through experimental data.
The pursuit of a theory of everything is a long-term scientific endeavor, and it is difficult to predict when or if such a theory will be discovered. Scientists continue to work on various approaches, including string theory, but it remains an open question in theoretical physics. Future developments and discoveries will shape our understanding of the universe, and it is possible that new insights may emerge in the coming years or decades.