Magistus said:
In all honesty, I don't see how. I personally have bought both, if I like the PDF and think the content is worth having at the game table I have then gone out and bought the book. And I know of a few people that have done the same. Now with Mongoose I am waiting quite a while for you to release the PDF to purchase it, and then figure if I want the book.
Magistus and myself may not be the norm, but I too buy both PDF and hardcopy and don't buy the hardcopy until I have read the PDF.
Admittedly I might buy some PDFs and then find the book isn't to my tastes (I bought Glorantha in PDF and read it but found it wasn't my cup of tea) but if I don't have the PDF I won't buy it at all.
So in mine and Magistus' case delaying the PDF actually delays us buying hardcopy from the stores.