Though they might get a bit more grief from non-readers before then who expect the finale will have the royal wedding the whole season's KL story arc built toward. And when they get it, after the euphoria of getting back at the Lannisters, they might come to miss Joffrey and Tywin as 'villains'. Cirsei's downfall isn't as strong.

They're gonna have a very strong early s4, though. Most of the material will be from the climax of the book, they can't lose.

I don't think they'll have problems with ADWD/AFFC either. Once the storylines are intertwined and adapted for TV, it should be pretty good. The books suffered from a lot of extra factors (frustration with absent story lines, no Tyrion, the extra long waits for each of those two books, probably too much time spent in Dorne at a point readers were eager for the existing arcs to progress etc.) that the TV series should easily bypass.