Ironically, I seem to remember seeing Conoco(Motorcraft's supplier)talking about a "fully synthetic" 5W-20. I checked on their site for more detailed info and couldn't find anything else about it. And realisticaly if they do come out with a "fully synthetic" 5W-20 it will most likely be a Group III and not PAO. Because I don't think Conoco is into making PAO oil. Could be wrong through. At this point in time I believe their's and Motorcraft's 5W-20 is a blend of Group II+ and Group III. I don't think you'll notice much too difference in the two oil's performance over a 5,000-7,500 mile OCI. But I'm sure it's safe bet to say that the price of the "fully syntetic" will be substantially more than the current blend.
Whimsey