From the monthly archives:

February 2013

Sony Alpha a58 is NOT an updated a57 rather a37

by Bruce on February 22, 2013

While the media and rumor sites are reporting that the Alpha a58 is a replacement for the a57, it is really just a barely upgraded a37. The model number should be a38.  Take a look at the specs, it has the same screen resolution and ISO sensitivity as the 37 while the 57 has double of both of those specifications. The continuous shooting speed is also less on the a58, very close to the 37. And as if that wasn’t proof enough, the screen tilts like the a37 as opposed to tilt and swivel on the a57. The only improvements over the a57 is the megapixel count and the oled viewfinder, neither of which really matter a whole lot to me. It also has a spot on the dial for effects, and a new feature called Auto Object Framing which could be nice.  Why am I the only one to notice this.

here and here for example