I wouldn't say we Sony fans are over confident. We are just confident. If anything, I would say it may be a lack of confidence from the fans of Nintendo and MS.
It's pretty obvious why Nintendo fans are worried. The Wii U started selling like a dying console only two months after release. This means that Nintendo fans rushed out and bought it, but the majority of the general gaming public aren't exactly interested in it. More games and a $199-249 price tag will help, but I doubt it will push it to #1.
For MS fans, they have seen the direction MS has been taking the last 2 or so years (focusing more on Kinect/casual games, while giving the core gamer just a game or two per year), and rumors are suggesting that the NeXbox will probably have the same focus. Not as powerful as the PS4 and Kinect in every box. Rare just revealed that they plan to announce a big Kinect game in the near future and Jonathan Blow stated MS seemed more focused on the multimedia aspects of the console when he spoke with them. The problem with this focus is that it seems that casuals may not be there in the same numbers as they were this gen (Wii U sales) and it is also going to drive some 360 core gamers to Sony.
For Sony, people are seeing that they have learned from their mistakes. Powerful system that's easy to develop on this time, so quality multiplats and exclusives from the get go, but will cost less than the PS3's $499. The Share features are also peaking people's interest. We all know what happens when Sony has a strong launch. Heck, Sony had one of the weakest launches ever this gen and they are going to finish a close 2nd to the Wii.
