Ok, I think there are 2 different ideas getting mixed up here. Just because some of us think that Tim is a great footballer does not necessarily mean that we think it would be a good idea for him to return to EFC (on loan). Personally, I think (just like his heading ability) that his timing in leaving us was perfect. His move to MLS was great for him and his family and for both personal and professional reasons he would be crazy to return to EPL. He has basically ruled that out himself anyway.
Having said that, I think Cahill is one of those players who continues to surprise. I had assumed that when he left and went to MLS that it would just be his last pay day and that he would (and should) retire from international football. However I, and many others who held the same views, have been proven wrong. He has been outstanding in both MLS and international football. His ability to score from all different positions (compare these goals WC v Holland, o/head via China, header v China, fastest goal in MLS) is unbelievable. Despite what has been said earlier, he does work his proverbial off and he puts his body on the line in any game that I have seen. This from a 35 yo playing in midfield or up front and usually marked by 2-3 players. Not sure what your definition of "world class" is but he has scored the same no of goals in WCs as Messi, Geoff Hurst, Platini and more than Ronaldo and many others. This is in arguably much weaker teams. Maybe we can borrow a much used phrase and agree that he is PHENOMENAL!