I know this is a slightly older thread, but I just now came upon it and figured I'd throw my two cents in.
I got the 4790k "Devil's Canyon" CPU not too long after it came out (upgrading from a 4770k which I got right after launch) and I am still using it with an Asus Z87-Pro board. There's been a few different video cards paired to it over the years but at present I have a very fast OC'd 1080ti with it along with running the CPU a bit faster at 4.6GHz and the memory boosted a bit to 1866 with low latency timings.
I'm using an ultrawide curved monitor at 1440p... so I'm actually pushing quite a bit more pixels than standard 1440p and I have ZERO problem playing games like Destiny 2 with everything maxed out. With G-Sync enabled I'm buttery smooth and staying at the 100fps cap (the monitor can OC to 120 but I don't use that) in just about all situations and the lowest I've dipped is to about 60fps in REALLY intensive areas and that was literally only for a second or two at those times. If I don't use G-Sync I will typically max out the monitor's 144Hz refresh rate and spike to as much as 200-400fps for small periods in different areas as far as what my video card is putting out. That's insane!
Ideally I like a consistent picture so I keep G-Sync on and limit to the G-Sync cap. I like it. It looks and plays great.
All this said, I don't see a problem. I suppose I'd never dip below 90-100fps with a newer CPU, etc... but I seriously doubt I'd see a difference. I just can't justify the expense of a new m'board, memory, ram and possible cooling solution when I am not compromising a thing right now. This CPU is still great for gaming IMO.
I too keep being haunted by the fact that I've had this thing for over 4.5 years... but damn, it just keeps on ticking! I do wish it were a bit better of an overclocker. With the memory controller and voltage regulator being on-chip it's pretty touchy beyond a modest OC. I've had
decent stability at 4.8GHz but that was literally pushing it (still had an occasional crash after a few hours... maybe could've tweaked it some more, who knows ?). Overclocking memory is difficult with this CPU too as a result of everything I just mentioned. To that end I will not be trying to stretch more life out of this system once I do start seeing a performance hit with new games, etc.
I'll upgrade... but not until I need to. I just wish they made RGB DDR3 like they do the DDR4 lol. But oh well.
One last thing regarding memory... I know there is more theoretical bandwidth with DDR4 but (until recently with better clocks overall I believe) I haven't seen any real world big advantage of DDR4 over DDR3 systems given that DDR4 requires sooo many more timing cycles to reliably write and read data - increase the bus speed but hit it up more for the same operations... almost balances out in many cases. As a tech for a living I've had the opportunity to test at least a few scenarios and the real world difference seemed marginal at the time, at least for average use and the gaming I like to do.
So... all in all if you have no need to upgrade because of something very apparently affecting you then I would stay with what you have and get a cool case and some lighting, etc.