If 40K had a scaled down rule set that was a small/skirmish scale (6 - 10 models) at a comparable price point to other skirmish games (Guild Ball/Malifaux/Bushido/Infinity/etc) it would experience increased growth from both new and experienced gamers. This would also open up the opportunity to expand forces within a faction to full army size by shifting those skirmish models to character leaders (army or squad leaders) and adding troop squads. This is what WWX seems to be aiming for but has had issues getting traction. Successful mini-wargame releases over the past 5 years have amply demonstrated the success of a character filled, affordable, skirmish scale game over the GW game model. This would be a great thing to see GW move to (40K-light), but I don't believe the behemoth can change it's current model sufficiently fast enough to make a difference.
Then again, isn't 40K a scaled down game now? The last game I saw at my FLGS was 4 "mini-titans" facing a land speeder and single 15 model wolf and other crap squad. 6 units on the table, which probably cost an arm, leg, and two fingers to buy at GW prices.
It just needs a lower priced entry point, not necessarily a scaled down version of the game. A better starter set and some more reasonably priced models are all that's needed.