Macotakara, a Japanese blog, are rumoring that Apple will release an "iPhone 4S" in July or August this year with the same form factor as the current iPhone 4, with a a completely new model, or "iPhone 5" not be launched until Spring 2012 (!). The main difference will be in the hardware inside the phone. They claim that the iPhone 4s will have an 8-megapixel camera, an Apple A5 chipset based on the ARM Cortex-A9 CPU, and will have a built-in SIM and thus not require the card.
The Arm Cortex-A9 is the same CPU foundation that is currently inside the iPad 2 as the dual core A5; however this does not necessarily mean that it will be a dual core in the iPhone 4s. If this rumor turns out to be true, it could still be a single core. Other rumors however do point to it being a dual core as we have heard previously that certain game developers were receiving these to test.
The SIM-less part of the rumor is apparently to integrate both GSM and CDMA technologies into the same handset. An improved antennae design is also rumored with 3-4 additional antennas inside. However, European carriers do not want this at all -- they feel it will get in the way of their customer relationship -- and so more recent rumors suggest [Apple may be working on something even smaller than the current micro-SIM.
As with all these rumors, take them with a huge grain of salt. Not long to wait now until all will be revealed officially or not, at WWDC. We will be there to see everything unfold. If this one turns out to be true, will you be upgrading; if you already have an iPhone 4? Will you just wait until next year for the iPhone 5? Let us know in the comments!