A citizen will lose citizenship of India if he acquires citizenship of some other country. There is no other reason for which citizenship may be terminated.
Atal Behai Vajpayee had planned for double citizens for Indians settled abroad. U.S.A. and some countries give honorary citizenship to some dignitaries. M.S. Oberoi is an eminent Indian citizen and Hotelier, who was granted Honorary citizenship by U.S.A.
India doesn't facilitate with dual citizenship.All the NRIs who attains the citizenship of other country and PIOs (Person of Indian Origin) can get Indian citizenship