We're together until death. CORRECT GRAMMAR [WE ARE TOGETHER... SUGGESTS THE FUTURE TENSE = WE WILL BE TOGETHER UNTIL DEATH] [THE FUTURE TENSE WOULD BE BETTER] Let's stay together until death. CORRECT GRAMMAR If we are destined to win, then we will win. CORRECT You are destined to become a champion. CORRECT If we are destined to meet, we will meet again someday. CORRECT [BUT "If we are destined to meet (implies/suggest meeting for the first time)] ["we will meet again" suggests meeting for one more time, which can only be true if the two people had already met at least once in the past]