Let us look at what the latest is in PC's
In the budget price range, have I7 with 4 cored/8 HT? Check
Have USB 3 ports? Check - new standard can be added with expansion card
Have multiple PCI-E 3.0 slots where video card gets at least X16? Check
Sata 3 ports? Check - although I do agree the newest PCIE NVME are great, even a Samsung 850 will be fast enough
Sound? Most motherboards are fine, but furthermore, many wear USB headsets so not an issue.
Gigabit ethernet? Check
I used to upgrade all the time as there WAS a compelling reason to go 8088 - 286 - 386 - 486DX - Pentium - Pentium II - Pentium III, etc. Also, AGP - PCIe, etc also were major improvements. The truth is we have stagnated. I no longer upgrade my machines (I build my own), and for server, I buy 2-3 year old servers (used to build my own, but better value used) at rock bottom prices with 32 cores and 192 GB RAM as new performance again is not that exponentially great (unless you spend $20-$30K.
You will NOT see a major bump until something that really increases the need comes out (NOT VR) such as PCIE 4 (even 5 may come out shortly after 4), or new storage methods, etc. Whatever happened to Hologram storage, fiber CPU's, or quantum computing that was just around the "corner" as those would also be compelling reasons. Heck even a I7-2600 still performs well. This article comes out quite a bit, but the answer remains the same: a saturated market will need a compelling reason to upgrade.
Now since laptops are not easy to upgrade (with a few exceptions), I can see those being purchased more frequently than a desktop - ie you need to go to faster GPU, 4K touch screen, etc., you need to buy a new laptop,