"I'll be right back!" - Jesus (so, what happened)?

Jesus is recorded as saying in Matthew 16:28: "...there shall be some standing here, which shall not taste of death, till they see the Son of Man coming in his kingdom." In Matthew 24:34, Jesus is recorded as saying: "...This generation shall not p, till all these things be fulfilled." Since the life expectancy in those days was little over 30 years, Jesus appears to have predicted his second coming would be sometime during the 1st century. So... what happened?