It might be worth noting that M1 Macs actually has two Thunderbolt controllers for 2 ports (dedicated controller for each port), whereas previous Macs shared two Thunderbolt controllers for 4 ports. The 2 ports limitation feels to me like a design decision rather than a hardware limitation (to differentiate with an upcoming higher-end model?)
The entry level MacBook Pro has always had only 2 ports, so this fits with the existing lineup. Most likely the next models to switch to ARM will get 4, like they do now.
There's a recently announced OWC Thunderbolt Hub[1]. I would still prefer to have 4 ports built-in even with two controllers rather than having to deal with hubs, though.
I did see this and it’s a bit sad that it’s been like 4 years since type c has come and hubs still aren’t generally available (even if just for USB and not thunderbolt). I mean I didn’t fully adopt USB type C just to convert the ports back to type A.
Before USB 4, USB-C spec itself say "see also USB 3.1" for USB hubs and disallow passing through Alternate Modes (e.g. Thunderbolt/DisplayPort) or Accessory Modes (e.g. audio dongle) which vastly limited the usability of USB-C port. USB 4 introduces a new discovery protocol with added support for passing through Alternate Mode in USB-C spec (as long as downstream is also USB 4).
My understanding is that daisy chaining doesn't require a mixed USB and Thunderbolt signal, only Thunderbolt. Before USB 4, USB-C spec itself disallows hubs to passthrough an Alternate Mode and even Thunderbolt daisy chain also have to terminate at any point where USB is plugged in. In this case, I believe you can have Thunderbolt 3 hub that only carries Thunderbolt signal, but it will only work with Thunderbolt devices and not USB-C.
But you don't need to mix signals. When you use a thunderbolt dock right now, doesn't it use pure thunderbolt as a backhaul, and have a PCIe-based USB 3 controller inside of it?
If that's right, then even without mixed signals you could have a pure-thunderbolt hub, and you could have a device with several thunderbolt ports and several USB 3 ports. And it should be straightforward to combine them into dual-purpose ports. The rules for passing through alternate modes don't matter because you're not passing through, you're not a USB hub, you have your own USB root.
That indeed could work, and it looks like Belkin's Thunderbolt 3 Express Dock HD[1] actually does this. Though in this case, Thunderbolt is limited to just 2 (1 for downstream and 1 for upstream).
I guess the biggest benefit of USB 4 hub is that allows the hub to have more than 2 Thunderbolt ports (the upcoming OWC Thunderbolt hub has 1 upstream and 3 downstream) and no longer have to worry about unplugging a device breaking a chain (usability problem).
