The games pushing the graphics limits of the ios hardware mainly game from big dev houses (Think ID, Activision, etc) The software pushing the limits of OSX mainly comes from big software house (Think Adobe or VMWare)

Despite it's success selling it's own software Apple would still have some massive problems if either Microsoft or Adobe announced that they were no longer developing for the Mac.

My knee-jerk reaction would be to agree, but I think it's also a matter of who can be helped the most. Smaller teams might not be able to afford extensive training from The Big Nerd Ranch or other outfits as much as larger corps might. So WWDC is certainly most useful to indie developers, but that doesn't mean Apple needs to market it expressly so.

Indeed. I think they are less important for WWDC as well. I've no doubt that the big companies can go visit the Apple Campus anytime they want and speak to the engineers as much as they want - they don't need WWDC