Im planning on making another computer around mid 2013.
These Are My Current Specs:
AMD FX 8120 @3.3GHz (With The Patches)
8GB DDR3 1600 RAM
1GB Sapphire Radeon HS 6870
I may get some extra RAM but that's it for this computer, I built it around 10 months ago.
So if you are wondering why I would upgrade that is simple, I really wan't 3D capabilites. Not just the fact I only have a 1GB card but it's AMD so my only choice is HD3D which has very few and very expensive monitors. That and I wan't minecraft to run faster which is where the CPU stuff is gonna come in, which minecraft does not use a lot of threads and it uses Java.
What I'm asking is what should I plan on building AMD or Intel? I know it's kinda a bit early to figure this out but I don't want to wait for something that's gonna be bad.
At this point, I would stick with AMD on the CPU. To jump to Intel will require a new mobo, processor and likely OS. Even then you will be jumping to a soon to be dead platform.
If you are looking to upgrade the CPU, would be looking at an FX-8350. Its roughly the same as a 3570k in gaming performance and wont require a new mobo or anything.
For the GPU you will need a stronger one outright if you want good 3D gaming performance, regardless if its from AMD or Nvidia. Though Nvidia cards and their bundled 3D software and system is a lot better than AMD's.
Its still pretty expensive, as a Nvidia 3D Vision capable monitor (a 120Hz monitor in a nutshell) can easily cost $300+, then throw in another $50 for the glasses.
EDIT: Just saw the time you were going to upgrade.
Definitely say Intel then. That is around the time Haswell (next big architecture of Intel CPU's) is being released, while the AMD Steamroller CPU's wouldn't be releasing till late 2013 on the (Not sure about this) AM4 socket.
On the GPU its up in the air. The Radeon 8000 series will have fully launched by then, and the new Nvidia 700 cards would start to be announced. Will have to wait till then to decide on this.