What did Jesus mean by "this generation will certainly not pass away.." in Matthew 24:34?

Matthew 24:34 says "I tell you the truth, this generation will certainly not pass away until all these things have happened.". I am a Christian, and it is my duty to seek out truth, not plainly accept what I hear or what other people say it is. So I've read this verse, and it really had me confused. Taking it by word and its plain meaning. I can read this as: - 'this generation' = people He was talking to - 'these things' = judgement day/end times It's clearly obvious that 'this generation' have already passed away, his disciples/followers/people at that time are already dead by now, and the world hasn't come to an end yet. What does this verse really mean? According to modern Protestant scholars.