With Apple going USB-C first, others will follow. Hopefully that will hasten the transition.
Hopefully. There's no guarantee - and the one place Apple
aren't pushing USB-C is the place where there is the most pressing need for it: Phones and mobile devices. Trouble is, only a minority of people need the sort of 20-40 Gbps you can get from TB3
on a laptop or SFF system. USB 3.1g1 is fast enough for individual disc drives, USB 3.1g2 is springing up in
USB-A connector form on PCs (the red ones) and DisplayPort 1.3/1.4 are coming, and will be far better for connecting 5k (or better) displays than the DP1.2 that TB3 (and USB-C driven by the Intel chipset) is limited to.
If the FCC hadn't made the call and issued a drop-dead date for the switch to HDTV, we'd still be straddling that gap, with lots of people hanging on to their analog picture tubes.
I don't know how it played out in the US, but here in the UK I'd had a DTV for 4-5 years before the switch-off was announced and, 5 years later when it actually
happened in my region I was on my second DTV (and it was getting hard to buy a TV that didn't have smart features & 3D - let alone digital). The switch deadline wasn't to create the market for DTVs - it was to flush out the last few hangouts, second sets in bedrooms etc. Plus, all the DTVs could receive analog just as well, and there was a £25 dongle to convert an Analog-only TV.
USB-A, HDMI, DIsplayPort are the current, mainstream ports that everybody is using. There's
one 5k TB3 display on the market and about 4 USB-C/UHD options. Only 1 TB3 dock (limited to 15W charge). Last time I looked, the 1m+"active" TB3 cables were still vapourware. This is in
no way comparable to the Analog TV switchoff and a couple of years too soon to
completely drop legacy ports.
When Apple went USB-only with the first iMacs, the ports they actually dropped were ADB (Apple proprietary keyboard/mouse connector), Localtalk (Apple proprietary), Serial/Printer/Modem (may-as-well-have-been-propitary RS422) and SCSI (
really bulky cables, device numbers, terminators, mainly expensive server-class drives) - there was a really, really pressing need to dump those for something
standard, plus, technology was moving faster and peripherals becoming obsolete sooner. Also, lots of PCs already had unused USB ports and ISTR Windows 98 provided the drivers, so the PC market was ripe to dump horrible kludges like the bidirectional printer port... USB-C.... not really so must-have.