Is it permissible to build a mosque or convert a building into a mosque in an area or city that is expected to become devoid of Muslims after some time, as happens in America where mosques are left deserted after Muslim students graduate and return to their home countries?

A building is constructed or converted into a mosque due to the public interest it serves for Muslims and for the manifestation of the rituals of Islam, and because of the hope that it will lead to an increase in the number of Muslims and the entry of some of the local inhabitants into Islam.