Thunderbolt for non-Mac types was never a thing and Apple is accelerating away from it. Look for USB-C to come into the spotlight.
I would disagree. We have some high-end HP portable workstations (i.e., 17" notebooks) that came equipped with actual Thunderbolt ports. I was able to use an Apple Gigabit Ethernet Thunderbolt dongle on the HP as a test and it worked (but in typical Windows fashion, after we downloaded the driver for it). The notebook did have built-in Gigabit Ethernet so it wasn't really necessary, but it was more to prove the point.
I do agree with you about USB-C, however. With Intel's Thunderbolt 3 using the USB type-C connector, Apple (and anyone else) can keep the built-in Thunderbolt support in the Intel chip sets and support multiple peripheral interface technologies through a single connector. There are a ton of things that Thunderbolt (effectively PCI-e over a serial connection) can do that USB 3+ can't.
For 90% of the user base, USB is the answer. It's everywhere, it's affordable, and it's "fast" enough for them. But when users like Don start throwing around 4K uncompressed video stream in their non-linear editing suites, they will appreciate the smooth, non interrupted delivery available over Thunderbolt interfaces. It doesn't matter if it's a Dell, Lenovo, HP, or Apple.