No, what happened is that HE was surprised by how much more interesting HE found Tywin Lannister, the Queen of Thorns, Littlefinger, etc... and how much he enjoyed writing their (now expanded) stories. People who were going to be throw-away "NPC" types suddenly became minor characters in their own right, and minor characters were unexpectedly vaulted into much more prominent roles.
I think one of the big issues with Books 4 and Book 5 is that Martin was struggling to make the non-Westros world (Mereen, etc.) as interesting as he had made the Westerosi. To combat this, I think he struggled to introduce a bunch of new characters, perhaps expecting that they would be just as interesting as, say, Tywin.