Like many here, I am a fan of the Song and Ice and Fire series and patiently waiting for the next book in the series: Dance of Dragons. At the same time I am wondering whether Martin will ever finish the series.
DOD is the fifth book in the series and the first four were released in 96,98,2000 and 2005. Clearly the gap has increased from two to five years. However DOD and the fourth book: Feast for Crows were originally one book which were split into two. IIRC a lot of DOD was already done when FFC was published so one might have guessed that it would take less than five years to write. And for some time it appeared that DOD would be available in 2008. So I am seriously beginning to wonder whether Martin really has a grip on his series. It's a vast sprawling epic with many moving parts and perhaps he has just lost control over the plot and doesn't know how to proceed.
The HBO series adds another twist. Assuming one year per book that means it will finish around 2016. At his current pace it doesn’t look likely that Martin will finish by then. However the series could induce Martin to at least write a treatment to finish off the series. If he doesn’t want to finish the novels himself he could commission someone else to write them based on the treatment. Not ideal but better than leaving the series dangling without an end.