My daily driver has the same RIVE x79 board with the Xeon E5-1680v2 (Ivy Bridge-Ep) which is similar to your CPU in single threaded performance, except the 1680v2 has 8 cores with 16 threads/virtual cores. The RIVE is one of the best overclocking motherboards for the x79/2011 platform so If you have a good CPU cooler then getting the 4960x to 4.5ghz won't be an issue.
Beforehand I had an overclocked Core i7-4930k and the Xeon E5-1660, in which case the 4930k is nearly the same as your 4960x. I only upgraded to the 8-core Xeon because it overclocks better than the 4930k and I can make use of an 8-core CPU. 6c/12t i7-8700k and 8c/16t i9-9900k aren't that far ahead of the 4960x and Xeon E5-1680v2 when these are overclocked to 4.5ghz.
This older 4960x HEDT CPU is more comparable to the 6-core Ryzen 5 1600x or 2600 than it is to any current Intel CPU. At stock speeds the 4960x is comparable to the Ryzen 5 1600x but with a good overclock it can compete with the Ryzen 5 2600 or 2600x depending on the clock speeds and memory speeds.
Most of the current 8th or 9th Generation Intel processors are ahead of the 4960x in single threaded performance, but the 4960x is a bit ahead of a Core i5-8600k or 9600k in multi-threaded performance. Your Core i7-4960x has Hyperthreading which gives your CPU a 2nd virtual core for every single core, while the current i5 processors does not, and this gives your CPU an advantage in multi-threaded applications.
As you know, the last BIOS update is 4901 but irregardless of that, the board still supports PCI-E 3.0 with your Ivy Bridge-E CPU and uses the UEFI firmware. Even if all cards that are out next year are PCI-E 4.0 compliant, you will still be able to upgrade to them because all versions of PCI-E such as 1.0, 4.0, etc are all backward and forwards compatible. Almost 2 years ago I was running a GTX 970 and GTX 1070 in an old AM2 motherboard which uses PCI-E 1.0. The UEFI firmware is an important feature because there are some graphics cards on the market that won't work with the older BIOS type of firmware.
There are still a lot of people who are rolling with their x79 setups because these are still doing very well for gaming. Now, if you're looking to push your framerates up because you have a 144hz display then maybe the current Core i7 or perhaps the newer Ryzen 3000 series processors might serve you better. But for 60fps gaming, the 4960x still does well even with a card like the RTX 2080. The 4960x should be able to overclock to 4.6ghz to 4.8ghz at 1.35v.
Games are moving towards using more cores and threads so I think you'll be fine for quite some time. Up until last year my son was running a GTX 1080ti in my RIVE system with an overclocked 4930k and he had no issues with any of the games he played and he was quite happy with it. Of course it's hard to predict what the future might bring because multi-core processors are getting cheaper and the expensive one are packing more cores. You should be able to get 2-4 years out of it as a high performance machine and the 4960x should be able to play the newer PC games for 5 to maybe 7 more years.
There are a small number of online forum threads that are dedicated to the Rampage IV line, so I would suggest checking those out. There is a lot you can still do with what you have so you might as well enjoy it. I wouldn't suggest buying anything until the x79 platform is obsolete which should be in a few years if not longer. Also, the speculation behind AMD's new Ryzen 3000 series has done a lot to drop prices of used hardware. The Xeon E5-1680 v2 that I have was $700 a couple years ago, and it was well over $300 at the beginning of the year but now it's $220 on ebay.