An i5 4690 should get you at least 3-5 good years of gaming. You're likely to upgrade your GPU before your CPU.
Unless you're running high-end multi-GPU setups, the 4690k will be more than fine in a single card or mid-end SLI / Crossfire setup. CPU generations don't scale in performance like they used to; before, you used to see a doubling of performance every 2 years or so, but it's not like that these days. It will be about 2-3 generations from the 4690 that you'll notice any kind of significant performance difference.
To give you some perspective, I used an i7-940 for gaming for almost 7 years, first with dual Radeon HD 4850s in Crossfire, then with dual Radeon 6950s and more recently with the dual R9 280x's that made it to my...