"A blank computer screen awaits," isn't the same thing as "Sitting staring at a blank computer screen,"

I think you're starting to read a little bit too much into every innocuous statement he makes. Someone else on the blog seemed to start panicking because GRRM said, "Plenty of story left to tell," when GRRM was referring to the rest of the ASoIaF universe as a whole (ADWD+2 more novels+unknown number of short stories+world book), not ADWD alone.

Some good news: at Comic-Con Bantam apparently told all-comers that if George hands in the book before the end of August, they think they can get it out in November. They didn't promise it, but they said they'd move heaven and earth to do it. They also said they think that outcome is entirely possible, but not certain.

Very cautious statements, but I think overall encouraging.