The word you want is probably "adventist". With an uppercase "A" it refers to the particular sect (Seventh Day Adventists); with a lowercase "a" it is anyone who believes that Christ will return, and hence is waiting for him to appear.
Adventist, n.Etymology: (advent n. + -ist suffix.)
A member of any of various Christian sects emphasizing belief in the imminent Second Coming of Christ; spec. a follower of William Miller (1782–1849), who predicted that the Second Coming of Christ and the end of the present world order would take place between 21 March 1843 and 21 March 1844...
1843 Signs of Times 15 Nov. 109/3 Publications have been sent to every English and American Mission in the world... The English Adventists, have also, for the last twenty odd years, been engaged in the same work.
2004 P. de Rosa Fatal Flaw of Christianity ix. 234 Since then, there have always been adventist or millenarian sects who predicted the end of the world and thousand-year reign of the saints.