Flickr user David Pickett (fallentomato) posted the below photo showing the differences between the male and female minidolls:

I haven’t opened up 3315 Olivia’s House yet so I haven’t discovered this on my own so big thanks go to fallentomato for the image. I can only assume that more male minidolls will be made in the future. But looking at 2013 sets, there aren’t any more so far and Peter can’t be the only male living in Heartlake City. Molds are expensive and I’m sure LEGO is going to want to recoup the cost of making Peter as much as possible.