Apparently when George R.R. Martin started A Song of Ice and Fire he expected it to be, surprise surprise, a triology, but of course it's ended up much longer. He said after a Storm of Swords (book three) that there would be six books total. However he also said the fourth book would start five years after the third. So many fans objected to this that he stopped midway through "a Dance with Dragons" so he could go back and write "A Feast for Crows" to cover the gap. This seems to be what caused the huge five year gap since the last book came out. On the plus side "a Dance with Dragons" is _supposed_ to be coming out in the spring of next year. I'd be a little more doubtful, especially given all the false promises made about the release of the fourth book, except that it's not the first time he's done this. There was a three year gap between books one and two but two and three were out within a year of each other.
Of course the situation is somewhat complicated in that a Feast for Crows grew so big that he's had to move a lot of it over to a Dance with Dragons to keep the book to a reasonable size. He bumped the expected book count up to seven because of a Feast for Crows, but won't there have to be yet _another_ book to account for the spillover from a Dance with Dragons due to the new material from a Feast for Crows getting tacked onto the front?
But anyways, If he holds true to the timeline i wonder if a Feast for Crows is even going to be out in paperback before a Dance with Dragons comes out. Not that i'm going to wait for paperback, i'm going to be bad and give into temptation and order them both from SFBC. I'm anxiously dreading finding out who he's killed off in the next two books =P