As most people likely realize, the Bible is full of symbolism, metaphor and allegory. How should we understand Genesis 4:10, where God said to Cain after he killed his brother: "Listen! Your brother's blood is crying out to be from the ground?" Are we to suppose that blood has some special capacity we are not aware of that allows blood to silently communicate with God? Is it not more reasonable that the account in Genesis is simply a graphic way of saying that Abel's spilled blood demanded God to establish justice in his case by avenging his murder?
Since that is obviously the case, Revelation 6:9 uses that same sort of allusion to symbolize how Jehovah must eventually avenge the deaths of his chosen ones at the war of Armageddon. Besides, the Bible clearly teaches that the dead are asleep in the ground until the return of Christ. There is simply no allowance in scripture for any soul to join Christ in heaven before that time.