Nothing lasts forever.  That is a hard truth that we face regularly as humans.  Buildings crumble, governments fail, and churches die.  We are not omniscient and so we are unable to plan for every event or anticipate every outcome.  A persecuted church can be tempted to think that God's plan has been disrupted, they can feel abandoned by God.  But Peter encourages his audience with the hope of their salvation, a certain anticipation that God will fulfill all his promises.  He is omniscient and omnipotent and there is nothing that can disrupt his good and perfect plans for our salvation.  We can rest assured in the security of our salvation because God has saved us and God is guarding us.  What God starts, he finishes.