This is a great question, in order to answer the question there is a lot to consider with regard to the order of the books.
There seems to be a lot of agreement that the letters were sent in the order that we read them in the scriptures, so I won't deal with that, but when I try to see how it could be the other way around (ie. 2 Thes and then 1 Thes) What I can see is that in Acts 17:1-10 Paul and Silas were together and travelled through Thessalonica on their journey. According to 1 Thes 3:1-3 we learn that Paul had sent Timothy previously to the church at Thessalonica. Did he go empty handed, or carrying a letter from Paul? 2 Thes 1 begins with a greeting from Paul, Silvanus and Timothy. Is this evidence enough to say that this letter was carried by Timothy to the church at Thessalonica before the other letter? I don't think this is conclusive, but it is great for us to think about. It also makes sense that Paul makes the note in 2 Thes 3:17 if this is the first letter they are receiving from him.
If we consider 2nd Thes. as the first letter sent out then Bruce's postulation that
since apocalyptic imagery is more widely used in Thessalonians than in the later letters, it is possible that the apostle came to realize that this was not the most adequate vehicle for expressing the Christian hope.
Our decisions regarding how we use eschatology in teaching the gospel and when and how we bring it into discussions with both believers and unbelievers is probably going to be affected as we see how Paul changed his strategies of trying to teach about the Christian HOPE. The order of books does not change the message of the HOPE we are offered, but perhaps more on the WAY that we as proclaimers of that HOPE do our duty.