As I see it, there are two options here. Either the author of the Jesus fragment got hold of Codex II before it went into the jar in Nag Hammadi in the late fourth century to be buried for 1500 years, or s/he got hold of it after it came out of the jar in 1945. While we cannot rule out the possibility that s/he got hold of Codex II before it went into the jar, it is much more likely that the author got hold of it in the modern period with its multiple reproductions, in print and internet, of that one witness.And therefore the GJW is a modern fake.
I'm sure the discussion will continue in the blogosphere and perhaps sporadically in the media, but most or all of this will probably amount to wheel spinning until we get some new information, most probably the results on the test(s) of the composition of the ink used to write the text. I myself am not an expert on materials science of ancient manuscripts and I do not know how definitive the results of such tests would be in principle. Is it possible to fake the composition of ancient ink? Can ancient ink recovered, say, in an excavated ancient inkwell be rehydrated and used undetectably to create a modern forgery? I don't know. If the ink turns out to be modern, that should settle the discussion in favor of the GJW being a modern fake, which seems to be the most widely held view at present. If the ink appears to be ancient, the questions above will have to be asked and the probabilities weighed.
As I've said from the beginning, I am very skeptical about its authenticity. But we'll see where new information leads us when we get it.
Background here and links.