hdmi is nowhere near the usb3, it just doesnt have the same use, the same functionality
why would apple put hdmi in iMac? what use would it have? they already have thunderbolt which incorporates display and data, hdmi is only video (display), nothing more
apple is all about less is more (minimalism) why would you have two different ports (hdmi + thunderbolt) when you can have all in one (thunderbolt) and they knew this from the beginning...
but usb is a whole different story, and usb3 is natural evolution of usb ports, and apple doesnt have to do anything aside implement ivy bridge to support it, even intel says that thunderbolt and usb3 supplement each other, hence why there'll be support for it in ivy bridge...
usb is already there, they just need to upgrade the standard, from 2.1 to 3.0, like they will be doing with thunderbolt when optical cables arrive, usb 3 is not a new port, its just an evolution of the port that already exists, and they were waiting for support from intel so they dont need to put 3rd party accessories to support it, again very apple-like - less is more
im willing to put a 1000 dollars that macs with ivy bridge will support usb 3, and im also pretty sure that all of the usb ports will be 3.0 standard, if i could make money on this kind of things i would already be a millionaire
really, usb3 is a no-brainer, its 100% if they implement ivy bridge, agree?
if you wanna look at past habits, look how fast they implemented usb 2, that should provide some insight
and thunderbolt to usb3 doesnt make sense, thats why they dont exist yet, and i dont think they ever will, why would you want to hook up your usb key to usb3 - thunderbolt adapter?
and imac 32' wont happen, the reason they discontinued 30' cinema display is because they thought its too big, if you want bigger, you can have 2 cinema displays, hence thunderbolt, more people will buy 27' than 30' for a computer, and thats all that matters, don't you think?
You make a good case for USB 3, and I surely hope you'll be proven right. But for some reasons, even if Intel says they're both meant to coexist, I don't see Apple offering both.
As you said "Apple's philosophy is less is more", and that's why they were so instrumental in developing Thunderbolt, I think their dream is that it replaces every other type of ports.
As for the 32" yes, you're right, it's too big for a computer display... unless the iMac 2012 is meant to be Apple's first foray into TV sets, in which case 32" is actually quite small.