I stand by my reply, but you're free to call MS and confirm this for yourself...
And you think that the customer service rep who answered the phone (and who almost certainly is not involved in development, distribution, packaging, etc.) will get it right? In all likelihood, they were given a fact sheet stating that each product contains both versions (which is their official line). I would be surprised if they knew if it was two separate DVDs or if it was just one DVD; they probably assumed the latter without even understanding what sort of major technical implications that would have.
Anyway, the correct answer here is two separate DVDs. First, because there have been Microsoft employees (who are not CSRs, but people with an actual technical involvement) who have posted in forums that it's separate. I don't have links to them off the top of my head, but that's what I recall reading.
Second, and perhaps most importantly, if you think about what needs to be done to make a dual-32/64 DVD possible, you will quickly, realize that there will be no such thing for W7 RTM. Maybe for a future SP, but definitely not for RTM.
Windows setup was simply not designed for a unified 32/64 combined disc. A non-trivial re-engineering of setup is
required for this to be possible. Let's say that between now and RTM, they do design a new setup that supports a dual 32/64 disc. Now what? They can't just deploy it. It needs extensive testing. Who's going to test this now that the Beta/RC is over? What about all the customer support people (not just at MSFT, but at various partners, IT depts, etc.) who have familiarized themselves with the 2-disc setup--MSFT is definitely not going to say, "oh, we were just kidding about the 2-disc stuff that we had posted during the Beta, RC, and TechNet RTM, here's the new 1-disc setup that we are actually going to ship and that we hadn't even mentioned to any of you until just now".
If you think about it, it will become clear just how very unlikely--to the point of impossibility--a combined disc will be. And it's not like having two separate discs is going to cost MSFT that much money, since dual-layer discs are more expensive to produce than single-layer discs, so there isn't a lot to be saved by converting two single-layer discs into one dual-layer (esp. when compared to the selling price of these retail packages).
As people have said again, and again, and again, what you get when you buy a retail package on October 22 is exactly what you see right now on MSDN and TechNet. And that's separate discs for each architecture and for each product level. Period. End of story. Anything else is bunk.
