Make a book that I actually enjoy reading.
To do that, they need to release a book with smaller font, more text, fewer unnecessary graphical frills, and which I writing which is at above the 6th grade level. The artwork needs to look like something better than that of a talented junior high student and needs to appeal to something other than junior high sensibilities. D&D used to be known for artwork that you could slap on the cover of a mainstream fantasy novel. No writer in his right mind would want to advertise his work with the sort of art 4e tries to advertise itself with.
I can't read the 4e books. They are boring and insipid. I find no joy in them. They are the first generation of D&D books that are actually boring to me. I used to enjoy going to a book store and pulling a gaming book off the shelf and reading it. I never do that with 4e anymore, and if I never read the books there will certainly be no excitement to play the games.
Some people will probably complain that they need all that crap to sell a book nowdays, because modern readers are just idiots who can't judge a book by its content. I disagree. Readers will always gravitate to content, regardless if they are 15, 25, or 50. Pictures may attract the eye or suggest a level of professionalism that suggests the book is worth reading, but within minutes of picking up a book pictures fade into the background and you mentally stop seeing them because you are reading the text. Too much time spent on artwork when that artwork crowds out content and makes the book expensive. Writing always trumps artwork, and the writing just isn't there. It's a snore. World of Warcraft can get away with bad writing and cartoonish graphics because WoW has wholly different focuses of gameplay and mental stimulus. For a PnP game, it's lethal. So yeah, some art is very good. But lots of art and bad writing is suggestive of badly misplaced priorities.
And the irony to me is that the art is so suggestive of lack of depth and maturity that its probably actually losing as much as its gaining in accessibility (again, PnP games will never be as accessible as WoW for the same reasons that text based MUDs will never be accessible as WoW dispite having almost identical game play).
Sure, this is a rant, but there was a brief time after 4e came out when I thought to myself, "You know, this isn't really the game for me, but it looks like it could be fun for certain things. Maybe I'll run a game." But that desire got killed by the deadly boringness of rule books.