So a few thoughts....
#1 - I am the originator of the 590 EX - PW Compatible rumor. I have also stated that I highly doubt Canon will do this, but if they did, I am certain they would sell AT LEAST DOUBLE the number of 590 EX flashes as they would using a proprietary radio.
Why is this? For one, PW has the LARGEST installation / Usage base IN THE WORLD. As an example, I will make this offer to the Odin zealots out there. I will give you $100 for every Odin user if you give me $10 for every PW user. I can tell you now, the check I WOULD RECEIVE would be enough to more than buy all the new bodies AND the new LENSES Canon has out there.
As well, this also opens Canon up to non Canon brands... all of the sudden Pentax, Nikon and other users who have PWs can add the Canon Flash.
#2 I see the comment "there are so many issues and complaints with PW and non for Odin" Seriously? See above. Odin has only been available in the US for a few weeks. I personally have not seen ONE on a store shelf, studio or in the field. I have, however, seen HUNDREDS of PW personally, especially when I was spending time in NY studio. If you have 1 million photographers using PW and a few hundred using Odins, which do you think you will see more blogs or post for... As well... Reading this forum alone, one would think that the 5DMKII was a total piece of crap, and while not perfect, there are a lot of photographers who not only use it regularly, but still love it.
#3 3rd party compatibility. Will Sekonic light meters fire off an Odin. NO. Will Odin trigger a Photogenic PL strobe? No. Norman? No. ProFoto? And yes, you can dangle an Odin off of many of these, but why bother, PW is BUILT IN to many of these monolights, devices, and packs.
#4 You cannot light meter with an Odin. As of right now, you cannot turn off the pre-flash, even in manual. I like to use my light meter, just the same as I spend 90% of my time in M on my camera and maybe 10% split between AV / TV. This pre-flash screws up light metering. True, many just use the histograms on the back, but still a lot of us like to dial in our shots
#5 The 580 issue, which some have experienced and others haven't was an issue with the 580, not the Flex. The 580 was a piece of junk when it comes to shielding and leaking RF, and while many try and blame PW for that, it was really Canon's issue, as well, shooting with a 580 on your hot shoe, that RF leak has the potential to add noise to your shots. Poorly shielded and leaking electronics are generally bad....
We will see what comes out of the 590 EX. If I were Canon, I would make the 590 EX PW compatible because of the HUGE user base for PW, the instant compatibility with brands like Sekonic, ProFoto, Photogenic, and Norman to name a few, the bigger incentive for 580 users to upgrade, as well as the ability for ANY Camera that has a HOT SHOE or Synch connection to be able to fire your flash out of the box. Probably won't happen, but then again, Canon is not necessarily known for brilliant moves, especially if you trust posts on this forum regarding Canon's responsiveness to Canon Design wants and matching Nikon.