Sony is holding a PlayStation event in New York on September 7th that according to some reports will be the reveal for two new PS4 models. One model is expected to be the already confirmed but still pretty secretive PS4 Neo/PS4K. The next model is expected to be the PS4 Slim. Sony has released a slimmer model of every PlayStation console to date (including to different PS3 models) so a slim PS4 has always been expected. It seems that someone may have their hands on an early slim PS4 ahead of its reveal and is already trying to sell it online:
If the image is legit (and it looks to be) then the system shares a similar design with the original but features rounded edges to go along with the slimmer design. It is unclear from the photo exactly where the HDD can be accessed for upgrades but I am sure that there will be more on that as new info surfaces.
Stay tuned for more details as they become available.