Same basic issue here: when I attempted to open images via the "Edit In" command in LR 5.5, the images would NOT open in Photoshop CC 2014. Initially I was trying to use the "Merge to Panorama in Photoshop" under the Edit In menu. If Photoshop was not already open, the program would automatically launch, however, the images did not open in Photoshop. I tried the Merge to Panorama command when Photoshop was already open, and it still did not work. I then tried other "Edit In" commands from LR 5.5, and I was not able to get any of the images to open in Photoshop CC 2014.
SOLUTION:
I uninstalled Photoshop CC 2014 and clicked the checkbox to remove the preferences in the uninstaller. I also went into my Library > Preferences and made sure to remove any other Photoshop preferences that were left behind by previous versions (I can't confirm that this step is required, but I took this extra step just to make sure). I then reinstalled Photoshop CC 2014.
I can confirm that I can now open images in Photoshop CC 2014 directly out of LR 5.5 using the "Edit In" menu. For me, the problem is now solved. However, it would be nice if Adobe could address this issue at some point to save this hassle for others who are upgrading.