The period during which the Quran was revelaed had a very harsh reality and it may perhaps be fair to say that humanity was in the stoneage compared to what it is now. Hence it might follow that we today may find some of the passages of the Quran harsh and innapropriate, whereas these passages may in fact may have been apporpiate/necessary to deal with specific situations of that time. Hence it is possible that passages such as 4:34, cutting off the hands of thieves, flogging of adulterers, encouraging the freeing rather than banning of slavery, for whatever reason they were ordained without sepculating on the details, was done only to contend with very specific relevant conditions at the time.
I agree, I dont think Muhammeds intention was long term. Otherwise he would also have decided on his successor. I think he didnt becase he thought it would have been a thorny issue with the rival contenders.
Indeed, the Quran itself says that it was sent down as a 'mercy' to mankind rather than something that we absolutely needed to live good lives. Another argument that one might make to support this general veiw is that Muhammad, it appears, made no attempt to compile the Quran as a single book before he died - something that we might have expected if if the Qur'an was indeed meant to be an eternal guide for the whole of humanity.
I would have also expected him to keep Europe, Australia or other parts of the globe relevant in the Quran, if that indeed were to be the final book. For example Iceland does not have sunrise & sunset everyday, but at times every six months. So what are they supposed to do during the month of ramadhan? Starve to death? On the other hand, other issues like water are overly mentioned when only parts of the world would have been suffering from drought like conditions like Arabia.
In my opinion, religion has played a major role in shaping our civilisations for the greater good over the course of our very long history - without it I'm not sure where humanity would be now. Maybe that was the purpose of religion and God's intention - religion helped shape humanity into what it is now but we were eventually meant to learn to rely on our souls and intellect to decide on good/bad right/wrong.
As you know, the vast vast majority of the quran is spoken as if its a direct instruction to people who are around him about the here & now, so I would agree. It does say that its a book forever, but I think was intended to show that it was a special book that would outlive their years, and was to show how important the words were.