I mentioned the ports 1) that "users actually need" in the sense "many people often use"
Many people often use DisplayPort and Ethernet. Also, FYI saying "all" as in "all the special use cases users actually need" doesn't mean "something that many people use". It means all. The hint is that you used the word.. "all". Well unless you're going to arbitrarily decide what people "need"?
The fourth commonly used port (Ethernet) would require making the laptop thicker, so adding it would probably be a poor trade-off.
As I've mentioned multiple times, every Mac mini since 2018 is 'hobbled', with 1 video output channel
forced to the HDMI port. The Intel mini supports 3 displays, but 1 has to be HDMI. The M1 mini supports two, but 1 has to be HDMI.
The 2019 16" MBP will run 2x 4K or 1x6K over TB3/USB-C (which you can connect to a TB3/USB-C/DP/HDMI/DVI/VGA display of your choosing) in addition to the built in display. If a hypothetical 2021 replacement added HDMI, but meant that the "second" 4K display had to connect via HDMI, would you consider that a "pretty obvious choice" or "a poor trade-off".
I've been asking that same question for almost as long as this rumour has been discussed, and so far I've not found a single person who's arguing for HDMI ports, willing to even acknowledge that it's a possible outcome if Apple were to add back HDMI. Not one. Most ignore it, one started going on about magic 8 balls and how "Apples new SoC means they can do what they want" while ignoring the Silicon elephant in the room that is the M1 Mini.
So, how say you: is trading 'universal' functionality (i.e. being able to run
all displays via a TB3/USB-C port) for a "special case" port that "steals" one output (HDMI, or DisplayPort, or anything - I'm actually equally opposed to any non-universal, high speed ports at this point) worth it, with the acknowledgement that it'll negatively affect those who don't use that port?
What about data? - Let's say they were going to add two USB3.2 10Gbit ports, a 10Gbit ethernet port, and a modern card reader (that isn't hobbled by an internal USB2 bus like the 2015 one was). That's pretty close to the bandwidth for an entire extra TB3 port (or technically a
pair of ports if they shared a controller like the previous models, but the expectation seems to be 1port = 1 controller with their new stuff). Is it worth it, to put in those single-use ports, either at the expense of one of the four TB3 ports (or controllers), or at the expense of an additional TB3 port (or controller)?