Can cyclic leukopenia develop into something more serious?

Need monitoring. The long-term concern is for major infections and sepsis episodes developing in these patients. Also, since these patients can be treated with g-csf injections there is concern for development of leukemias which are seen in patients with severe congenital neutropenia ( a related but different disorder).
Usually not, but... Very severe bacterial infection can occur and can be fatal. This needs to be watched closely; there are some biotech treatments that work. Often the disease remits after puberty. Best wishes.