If it's crap ... We'll tell you
They really can't use filler or go off on a tangent. If the books aren't ready all they can do is stop.
Now that the TV series is up and running we can only hope GRRM produces the next book in a shorter space of time, which isn't completely unlikely, it's only the last book that's taken a ridiculous amount of time.
I believe one more book is planned, which is likely to be split into two installments.