What will happen when GMax is no longer there is a favorite topic for discussion on forums for a while already now. One of the alternative modelling programs often mentioned is Blender. Personally I consider that a good alternative as it is open source and seems to have quite a big user base. A little while ago I bought a book about this tool and I am reading that now. When I have read enough I will start making some models in it to see how it works. The interface seems a bit hard to learn (but we heard to same about GMax, right?), but from the book it sounds quite easy to work with once you know how it works.
And some interesting news is that a first version of a FSX exporter for Blender has now appeared. I find this a very interesting development and look forward to contribute to this exporter once I have learned my way around in Blender. I’ll keep you posted about my progress.