Since the Thessalonians have turned from idols and worshiped the "living and true God" they now anticipated Jesus' return. They were living with the hope that Jesus would return soon and they anxiously awaited the day. I can understand how they felt. I look forward to Christ's return as well.
I know there are a lot of "theories" on how and when Christ will return. You have the Premillenial view, Postmillenial view and the Amillenial view (if you want to know what these words mean I would suggest you look them up or search them on Google). Theologians have argued for years about how and when Christ will return and I even have my beliefs and convictions. However there are people who have predicted dates and they have been wrong, others play it safe and predict an era or a generation when he will return and even others have made a nice living getting people all worried about the idea that we are living in the "end times". The truth is we don't know when Jesus will return. God's Word says, only God knows the day, the hour and the time. We can argue about when, where and how He will return and I personally think we just need to live our lives as though Jesus may return any day. I am not being irreverent but I don't really care how or when Jesus returns. I just want Him to return and I live in anticipation of that day.
Will there be a rapture? Will it be pre, mid or post trib? Will Jesus come back tomorrow? Will He be back today? I honestly don't know. I have actually stopped filling my mind with end times scenarios. All I know is Jesus will return some day (as the Bible says) and it will be a glorious day for the believer and it will be horrific for those who do not believe.
Random thought: Don't worry about tomorrow for tomorrow will take care of itself. Live your life in anticipation of the Lord's return today and be ready.