Recent fresh install of Windows (mainly use Linux but I wanted to play Witcher 3 again and no date on the Linux version yet) so everything is up to date. The CPU is fine, it's idling below the usual idle temperature and doesn't reach excessive heat under load.

This is new to me. Care to explain where the disadvantages of AMD-CPUs are, when it comes to Linux?
I'm using an old Athlon II triple core with Linux Mint and even GameCube (Dolphin) and PS2 (PCSX2) work quite well.
Is it about power saving?

Well, they obsoleted my on-board graphics in the Linux driver a few years ago. I eventually had to install a cheap Nvidia card instead. Intel generally seems to keep their drivers up to date, and I believe they're open source.

Actually AMD is working on a new driver system for linux that should be released till the end of this year and effectively remove linux driver issues.

More here: http://www.pcworld.com/article/2956567/components-graphics/amd-is-working-on-a-new-linux-graphics-driver-to-catch-up-with-nvidia.html

Bad time to upgrade old rigs. DDR4 boards for 1151 sockets are replacing the 1150 & the Graphic Card manufacturers are preparing for the newest versions. Depending on the financial situation I strongly suggest saving the few months till the next gen cards with HBM ram for upper/middle VGAs gets released & getting a complete new rig then.

Here the i5 Broadwell and Skylake's prices are quite similar.
Maybe only the GPU prices will drop significantly?

any recommendations for a new CPU would have to be for the motherboard socket you have. Otherwise, you are looking at a new motherboard and CPU. If you are giving your CPU to your friend, you need to make sure his motherboard has the same socket type. If you have different motherboards, you might have a irate friend who suddenly has to put out a extra hundred or more bucks to utilize the CPU. Other than that, I have no clue what to recommend for mid-range gaming since I just went with the heavy-duty 5930k (unlocked for OC but not OC'd) in a PC build in July with a Noctua heatsink (yea it cost a extra $100 for the heatsink but it gets the CPU down to sub-40 degrees clesius while idle).

I run an AMD FX-8350 its cheap 8 core and i can fully simulate another operating system while running API twitter calls and game without much issue at all.. also ram was cheap and i got 16gb.

retail comes with heatsink and ive never had thermal issues.

Price and performance are similar. The boost comes from the DDR4 Rams. If they act the same globally I don't think the GPU prices will fall much. nVidia usually keeps the price the same for low, mid & highend gaming cards. The high end cards are usually sold out before the next generation comes; could be a short phase of drop if someone had a to big stock of the last gen.

I'm well aware of the driver problems with AMD-GPUs and changed to an Nvidia card for Linux, but please notice, that this thread is about CPUs.

I hope so, the current prices are unbereable :|