you're in luck, the new generation the Ryzen [3,5,9] 3000 series CPUS and X570 chipset motherboards are finally breaking the generational gap. A decade ago I got an i7 desktop and it serves me well today. These new systems look to be (a) worth the upgrade, in terms of better performance, and (b) hopefully well made enough that some might last out another decade.
I don't know if Intel will manage to blight innovation and keep the market static as they have the last decade, or if the "upgrade cycle" will begin to make sense again down the road.
Also: 4k monitors are worth the price. Pixels will make you happy.
Finally, I advise spending at least twice what you initially think necessary for the mouse, keyboard, etc ancillary interface stuff. People skimp on these and then spend years with a crappy keyboard and growing RSI. Buy the good monitor stand and the wide mouse mat or fancy trackball or whatever.