Attempting a serious answer and avoiding all unlikely inducements (rare scotch or bourbon whiskeys, scantily clad women to deliver the rulebooks to my front door, etc.), here is what 4th edition would need to do for me:
1) I would need "The Great 4th Edition Encyclopedia of Updates." Essentially one to three massive products that go beyond the core rulebooks to provide me with
a) monster statistics for all monsters from all prior editions of the Dungeons and Dragons Game (no exceptions, not even for the flumph);
b) complete set of class/prestige class analogues for all prior edition classes, kits, and prestige classes;
c) complete statistics blocks for the litterally hundreds of NPCs from all prior adventures including those from Dungeon magazine;
d) magic item descriptions for every magic item from all prior editions of the game;
e) rules coverage for all the environmental/planar/psionic/high-leve-epic/ or other special circumstances that have been covered in prior editions of the game;
f) updates for every spell from every prior edition; and
g) just about every noteworthy adventure and Dungeon magazine issue adventure updated to the new rules.
I have NO TIME to spend updating my campaign any more. I have just enough time to comb through 3.0 and 3.5 resources to update those prior edition adventures I want to use. And I don't want to wait to the end of the 4th edition product line to get it all, spread out over twenty different resources and an online subscription service.
2) I would need a comprehensive Greyhawk resource adjusting the core rules to a Greyhawk that existed in a crystaline sphere known as Greyspace, nested at the center of the Planscape multiverse. (No need to delve into Mystara, Athas or any other crystal spheres - that can all be optional).
3) The price of these items, not to number more than 2-5 significantly-sized volumes, would have to be below $500 for the lot.
4) I might then buy further 4th edition materials since they would then have to introduce original material (and not another rendition of the Wild Mage or Thought Eater intermingled with some new material).