I'd not heard of this, so I did a quick Google.
The Wee Free Men: The Beginning is actually an omnibus of The Wee Free Men and A Hat Full of Sky, so it's basically two books in one.
I suspect they're planning to publish a second omnibus of Wintersmith and I Shall Wear Midnight.
Nullus Anxietas V - The Australian Discworld Convention
10-12 April 2015
Novotel Parramatta, New South Wales, Australiahttp://ausdwcon.org