I do not believe I misunderstood your post.
You did say that Adobe had changed the APIs did you not ?
I don't recall saying that, though my post above may have been unclear. Apple changed the printer driver APIs and requested both applications and printer drivers switch to using the new APIs. Adobe said "OK" and did so starting with CS4. Epson said "OK" and added support for the new interfaces in their Leopard drivers for RGB color printing, which works fine (though as Jeff noted above there is still a remaining glitch with the ABW side of the driver). Canon said "OK" and added support for the new interfaces as well in their Leopard drivers -- at least for some printers, such as their iPF series. It is unclear to me (i.e., I simply don't know) what they did with their older drivers (e.g., for Tiger), or whether they updated the drivers for the Pro9000 or iP4500.
OK. So how did Adobe make sure that the printer manufacturers were aware of this; and that they were aware that the changes could seriously effect the ability to create a colour managed workflow ?
As I mentioned above, it is Apple's API, not ours, so it has been Apple notifying the developers (including the ones at Adobe, Epson, Canon, HP, etc.) about API changes.
Did not Adobe test CS4 with different printers (or, at the very least, with a selection of professional printers) and identify this problem ? Having identified this problem did they make the manufacturers aware of this ? Did they post warnings on the internet and with the installation software so that users would be aware of the pitfalls ?
Yes, we have lots of printers internally from many different makers and we tested them printing from various platforms. I say "we" generally here because, although I am aware of the general procedure, I am not actually part of the PS dev team and hence don't know exactly which printers we have, and exactly which versions of the driver were tested, etc. I do know that we don't have every single printer made by the Big Three, so it is possible that, say, we don't have a iP4500 in-house and hence didn't test it directly.
My understanding, though, is that we also gave early builds of CS4 to the printer makers (e.g., Canon, Epson, HP, etc.) so that they could also test it with their own printers.
And there you go again, handing the problem 'over the wall'*.
May I respectfully suggest that it would be more constructive to engage in dialogue with Apple and the printer manufacturers and focus on providing a solution.
As I noted in my first post in this thread, we have already double-checked with Apple (actually even more times than that) that we are using their printer interfaces correctly. We have also worked with Apple to see if Photoshop can provide internal workarounds so that even if a driver isn't fully compliant, it will still print correctly. Unfortunately none of the workarounds were considered satisfactory (e.g., they would all break when Snow Leopard comes out, or if the printer driver version changes, etc.), and Apple strongly recommended that the real fix come from the drivers. We have also had direct dialogue with the printer makers with regards to driver issues, but ultimately they are the ones to decide whether or not they will update their drivers. Epson did so for their latest printers, Canon did so for their iPF-series printers, but possibly not for the iP4500/Pro9000.