I don't see this being a big upgrade. Hardware hasnt changed a lot in the past 24 months. They are currently selling with up to an i7 3.4ghz quad core and can be upgraded to 32gb of ram (not by apple, they will only sell 16). They will throw in a ssd and a regular drive if you want to mortgage your house to get it. I just looked at Intel's site and even the newest generation of the i7 is not much faster. I am sure it has a more detailed instruction set and I have noted that changes in processors in recent years have been less of a jump in MHZ and more of a jump in architecture for efficency. There is a potential for an upgrade in graphics as the chipsets there have changed as well as an upgrade of the screen. I could see apple building this computer with a retna display. Other than that I dont see where they are going to make a major change to the system unless its a aesthetic design change.
On another note. I helped a friend change a hard drive on his and if they do make a design change maybe moving the hard drive to somewhere that it can be accessed without complete disassembly of the computer would be awesome.. Make it like a hot swap drive bay from a server and put another metal cover down by where the memory is in the bottom. Not that Apple would ever want to make something easy to service. They never have.
On another note. I helped a friend change a hard drive on his and if they do make a design change maybe moving the hard drive to somewhere that it can be accessed without complete disassembly of the computer would be awesome.. Make it like a hot swap drive bay from a server and put another metal cover down by where the memory is in the bottom. Not that Apple would ever want to make something easy to service. They never have.