@Keyz
The problem is like you said that no one can tell you if future games will benefit or more cores or the AMD architecture.
For intel it seems to stay the same in the mainstream/performance market (Sockel 1150 and soon 1151) for a while, that's 4 cores for the i5 and 4 cores and hyperthreading for the i7. So I guess the games will still be optimized for 4 or less cores. There may be some that benefit of >4 cores (or threads) but I guess that will only be a few.
For AMD I truly don't know. Their Jaguar (currently in the PS4 and XBox One) architecture and the follow up the Puma architecture are low power oriented multimedia platforms. They are not very powerful (in comparison to the Core i series) and very unlikely to be suitable for a gaming desktop system.
The Richland (Piledriver) architecture does have a moderate performance and some models are quite nice for their price (Athlon II X4 760K) but again compared to the Core i series they are still less powerful.
And finally the (old) Bulldozer FX CPUs are a mixed bag.
On the plus side: they have up to 8 threads (FX-8xxx) they can work on and they have high clock speeds and even overclock some more and are not that expensive and in certain areas they really are able to perform pretty good.
On the down side: their single thread/core performance isn't very good compared to the Core i series and they perform not as good as the Intel CPUs in games. They also need a more power and produce more heat.
Maybe we will see a new FX series some time that is based on the Steamroller architecture. But I doubt that this will be a huge leap but rather a small step in the right direction. If a game is optimized for the FX and/or uses it's many threads the performance can be quite good, but the sad thing is that this is only sometimes the case.
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My recommendation if you want a gaming PC at the moment is:
Budget <800 USD
~200 USD - i5-4570
~ 70-75 USD - B85 Mainboard (like the ASRock B85M Pro3 [µATX] or the B85 Pro4 [ATX])
~ 65 USD - 8GB DDR3-1600 Kit (or single module if you only have 2 slots and want to upgrade later)
~ 60 USD - decent power supply 400-500W (like the Seasonic S12II 430B)
~ 55 USD - 500GB HDD (a SSD for the system drive would be a great option but will cost another 70-130 USD depending on size [120-256GB] and model)
~ 40-80 USD - a nice case (NZXT have some nice cheap ones, you may want at least one 120mm fan in the back and maybe USB 3.0 in the front)
~ 20 USD - a DVD RW (maybe a BluRay if needed, but that will cost more)
~ 210 USD - GeForce GTX760 or even a R9-280X if you can squeeze that in your budget (~ 270 USD)
Budget ~900-950 USD
If you want to overclock swap the i5-4570 with the i5-4670K and the B85 with a Z87 mainboard. That's about 40 USD more for the CPU and about 30-50 more on the mainboard depending on what you want.
Oh and for overclocking you would want a better cooler, like the Thermalright Macho HR02 or at least something like the Arctic Cooling Freezer i30 (~ 40 USD) or better.
Budget >1000 USD
I would spend that on the GPU. For gaming a i7 isn't really worth the money compared to that i5. A Radeon R9-290 has a lot bang for it's buck and a GTX780 is a great card too but rather expensive. For both you may want to get a model with a good cooling solution so that the R9-290 can reach and hold it's max. frequency without getting too loud and for the GTX780 to be able to overclock.
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Budget <600 USD
Swap out the above i5 with the i3-4130 (~ 125 USD) and maybe that B85 board with a H81 board (~ 50 USD).
So you have the ability to maybe later upgrade to a i5-4570 (or even i7-4790 if you feel to/need it or maybe a Xeon E3-1231-v3)
Swap that GPU with a R9-270 (~ 160 USD). Don't mind the 270x, that's the same with higher clock rates that you usually reach with a little overclocking.
If you really feel like going AMD you could swap the CPU and mainboard with:
~ 120 USD - FX-6300 and overclock it
~ 60-80 USD - a cheap 970 chipset board if you want only moderate overclocking or maybe a better one if you want to overclock higher (GigaByte 970A-UD3P for 85 USD or better)
Budget <550 USD
~ 90 USD - AMD Athlon II X4 760K
~ 45 USD - AMD A55 Chipset board - for overclocking I would suggest a 75 USD - A88X Chipset board (like the ASRock FM2A/88M Extreme4+)
Anything below that budget you would have to swap the GPU and for any half way decent 3D gaming I would not recommend anything below a GTX 750Ti or a R9-270.
