Here is my take on this...
Who cares?
I mean, there is already a lot of stuff out there on Magnamund, from the origional LW books (slowly but surely being done online by Project Aon) to all the fanfic that is being produced by Tower of the Sun. That says to me that the world is alive and kicking. Do we want to see this go into D&D style product overload? I do not think so.
While it is nice to have new suppliments, there is also a requirement for someone to write the suppliment, someone to edit the suppliment, people to playtest the suppliment, someone to publish the suppliment, someone to print the suppliment, someone to ship the suppliment and someone to sell the suppliment. I do not think that it is as easy as saying "lets publish a suppliment", and if in the end the suppliment does not sell, then they run the risk of financial failure.
Instead, I suggest this. Lets all start writing. The Wolf, in Tower of the Sun, has made a call for people to start submitting to S&P for publication, and while people are correct, S&P is not the same as having a book to open up to, because it is available in PDF, just print it out and add it to a binder.
If all of us fans started to submit stuff for S&P then all of a sudden thier would be a whole lot of stuff for all of us to use.
Just a thought, and hopefully my article on a Dwarf mining village in northern Bor makes the cut!
Al