OK, I'm going to say this at this point:

GW are publishing WFRP and, per statements made by the head of the
subcompany publishing and the head of the company contracted to design,
checking only setting text (names and rough abilities of spells, types
of career, views on orcs, etc). The rest is in Green Ronin's hands,
limited chiefly by the fact that if sales dry up they won't be
publishing more new books.

Green Ronin are the designers for this 40K trilogy of games, too. So
while we're looking at GW's attitude, let's also look at GR's record.

The True20 system is getting rave reviews for reinventing d20 into a
system with less panic about class abilities and a more
easily-customisable approach.

Mutants & Masterminds has reached second edition, and it's now the
second biggest game in the superhero systems league. This one has
supplements coming; I'm looking forward to the Mastermind's Manual - but
the core rules give you everything you need to play or GM a game.

The Freeport d20 setting is one of the best-received third party
settings and campaigns out there.

Then, of course, there's WFRP2.

Entirely playable using only the core rules; magic, godly magic, social
interaction, combat, a wide assortment of weapons, a reasonable
bestiary, a basic background to the Empire and environs.

With the exception of the godly magic (upcoming, I believe) and social
interaction, there have also been supplements on each of these sections,
plus adventure support.

Green Ronin's approach is to give players all that's needed to have a
solid campaign in the core book, and then to put out supplements that
are aimed at a high enough quality level that they're just worth getting
anyway.

>
> Another important factor is actually having a full set of rules to
> use. The press release already said that it will launch supplemental
> books over the course of years. So they are basically hobbling their
> players from the start. A typical dripfeed approach of Games Workshop.
>