I have use Aperture and CS 4-6 over the years processing thousands of pictures and still do. Occasionally, there have been problems, but overall, the combination has been an enormously powerful tool. I don't know if Aperture 4.0 will ever arrive (not sure there are new tools that need to be in Aperture), but if it does, it will mostly likely be more than than in incremental improvement.
Could it be? I just upgraded to Mavericks and Aperture 3.5. I sent one picture from Aperture to PS (Aperture set to export as .psd), made a simple change and saved it. OK so far. Sent the changed picture back to PS and made another simple change. Saved it. Voila! The file with both changes showed up in Aperture.
That is just one file and both changes were done straight onto the background layer so who knows what will happen when I try to save an image with multiple layers. There is, however, a glimmer of hope. I had already downloaded a trial version of Light Room but I would really rather stick with Aperture.