heathen....We have discussed this topic quite thoroughly in recent threads (and I see we have yet another Rapture thread being posted). The "great multitude" are not in heaven because heaven has come to earth. New Jerusalem and the Temple do not "come down from heaven" (note that it is not heaven itself but New Jerusalem/Paradise that descends) until the very end of the book (ch. 21-22), as following the creation of a new heavens and earth, after the first and second resurrection and after the millenium, as the presumed final end state for eternity. But before this, the Temple was "in heaven" for it does not descend until all things are made new, and yet a "great multitude" were already "in heaven" at the time Babylon the Great is condemned (see Revelation 19:1-2). You see the problem?
Paul, on the other hand, describes a heavenly ascension in 1 Thessalonians that occurs at the time of the resurrection and Paul only professes a heavenly hope and knows of no other "second destiny" (or even a materialistic chiliasm of the sort typified by 2 Baruch, Papias, Revelation, and Irenaeus).