"Our Guides to Raw Processing in CS3 & 4 have had remarkably little traction since their release - so we are quite leery about dedicating resources to a Guide to PS CS6 - especially one which might cover the same ground as Lightroom."
My two cents is that your most successful productions are those that are relatively unique to LL. "Camera to Print" and "Where are My Pictures" are examples of videos for which there are not many equivalent products, and for which your tutorial style is well suited. Your Lightroom Guides face more competition from some high quality "All Screenshot with Voiceover" tutorials, but you still have some differentiation based on a unique presentation format and your long history with the Adobe engineers. The Raw Processing tutorials don't really fit that description, and I guess I am not surprised that they have fared less well.
The first challenge in producing a tutorial on Photoshop itself is deciding what to cover. If you make it a straight PS photo editing workflow tutorial, I think you will have a limited market similar to the Raw Processing videos. If you try to cover more sophisticated editing techniques how do you decide which ones? And, there are many more alternative sources for those kind of editing tutorials, including very high quality videos from Adobe, Photoshop News, and various other independent sites. When I am trying to figure out how to perform a task or accomplish a specific effect in Photoshop, a simple Google search usually finds more than one good, clear, free explanation.
For what it is worth I have the Print, Asset Management and Lightroom videos, and all of the LLVJs. I did not buy the Raw Processing and would not by a Photoshop series. I would, however, look forward to seeing select sophisticated PS techniques covered in segments in LLVJs -- but the Journals would have to be released on a much more frequent and predictable timetable for that to take hold.
Only you all can decide whether the return on sales of LL Video Journals justifies your investment of time and resources, or whether there are enough interesting topics to fill journals on a frequent basis. Either way I would not count on a Photoshop series to have the same reception as your Print, Management and Lightroom productions.