If you look at the beastiary, until the 33rd, all visible are NPC's. Terraria has 26 NPC's at the moment. The Golfer and the Zoo-NPC are present. Means there are 28. Until 33 it is invisible if it could be an NPC. So that means there must be at least three more NPC's, to get it to 31. but maybe there are 2 more NPC's too. And the NPC's at the end aren't any that house. So there might be new NPC's, that are travelling around the world. Or maybe more.
So lets say, 31 NPC's in total, means there are 5 new NPC's in total. If 32 and 33 are also NPC's, then 6 or 7 new NPC's.
Maybe the Pet-NPC's will count as these.