This particular sonnet ends with a reference to Judgment Day or Doomsday ("doom" in line 12). In Christian teaching, there is a belief that eventually the world will be destroyed in a terrible fire -- at which time the forces of good will defeat the forces of evil (the idea of Armageddon). Also at this time all of mankind will have to face their Maker, God. God will judge each and every one of us and pronounce His judgement (or doom). God will decide who will be saved and live in Heaven and who will be condemned to spend eternity in Hell. The speaker -- as well as Shakespeare -- believes that his poem and all poetry will survive until that time. Only the forces of Heaven, only God, through the destruction of the Earth, has the ability to bring to an end the existence of any given poem.
In "Sonnet 60" Shakespeare continues the same theme. In this poem Time is once again personified and carrying a "scythe" (line 12). Time is once again described as a destructive force and is associated with death.
"Sonnet 65" also contributes to the same theme. Similar to "Sonnet 55," this poem compares fragile beauty ("summer's honey" in line 5) to objects that are seemingly much stronger and sturdier: rocks (in line 7) and gates made of steel (in line 8). But rocks can wear away (like the marble statues of the earlier sonnet) and steel gates can erode (like the gilded monuments of the earlier sonnet). But beauty outlives the rocks and steel gates when it is preserved in a poem.