can they force 343 to make ON Disc Locked DLC, and do you think they will?
In most if not all cases, your publisher decides when and how your DLC is released and for how much. Which is why the Bungie/Activision deal is monumental that Bungie gets to decide price and timing on their game.
Of course, the developer can attempt to put their foot down about some things, but it depends on how much sway they have on the publisher's management and how much money they've made for the publisher.
Microsoft made Bungie sit on DLC for almost 2 years (all the Mythic Maps were supposed to be part of a "Mythic Collection" for release in fall 2008 right after PAX, and the last ones didn't hit the public marketplace until February 2010) just so they could have something to upsell other Halo titles. Bungie couldn't acknowledge the existence of maps that were specifically named in the achievements from TU2 in September 2008.
Then we look at Halo Wars, which we can assume is entirely Microsoft controlled since they disbanded the original developer. The DLC has never gotten a permanent price drop and one of them is an unlock key. The DLC is 20$, and the game comes NEW for 30$, and it includes both the DLC as codes.
Johnson being pre-order only sounded like something MS wanted.
The Grunt Funeral Skull for Anniversary being pre-order only sounds like something MS would do. And I'm actually quite annoyed at that since it's actual gameplay, and not a skin/cosmetic like ODST and Reach's preorder stuff. It's stupid that something that actually changes gameplay will just be unavailable for people that didn't preorder the game. We'll have a split SLASO community from people that can turn everything but Grunt Funeral on and people that can include Grunt Funeral in SLASO runs. Know what would have been a good preorder bonus? The ability to unlock the Halo 1 nameplate in Reach.
At least Bungie didn't rub it in your face if you didn't get any exclusive unlocks. None of the pre-order only stuff from Gamestop shows up in your armory as locked away, the new-copy only Recon doesn't show up as locked away, the Legendary Flames don't show up as locked away, and none of them count towards your percentage. If you didn't play the beta, Bungie.net doesn't taunt you with a nameplate you can't unlock. Meanwhile, Gears shows greyed out locked slots for Beta stuff that just sits there, forever unattainable.
So if you want an indication for how Halo 4 DLC is going to go, look at Anniversary's pre-order DLC content.