Both Arianne chapters, plus the Victarion chapter where he finally reaches Slaver's Bay and the Tyrion chapter set at the same moment, were originally written for ADWD and moved out of it during the editing process. So if he's picked up the pace, it happened during the writing of ADWD, not since then. And I'm not convinced that two travelogue-heavy Arianne chapters during which the most significant event is Storm's End being captured, offstage, are a hopeful sign in terms of narrative momentum. At the very least, the opening chapters are going to overlap the end of ADWD, and move at that pace for a while.
I don't believe Martin has changed his stance on the publication date, which is that 2013 is out of the question but he's still hopeful for 2014. Personally I think 2015 is more likely, but we'll see.