The only problem with that is that it won't be able to reliably carry Thunderbolt 4 speeds. Most of those connectors are "USB-C" which is achievable, but I haven't seen any (verified) Thunderbolt 3 magnetic connectors, even.
That's important for Pro Display XDR users, or Thunderbolt dock users, who only use one cable to plug their Macbook in (power+thunderbolt).
Or, screw it, we end up with a charging only breakway USB-C port.
I mean, if they change the current USB-C to USB-C charging cable to a magnetic breakaway one, I imagine they'll increase the price of the cable if bought separately.
And if they move to the iPhone MagSafe charging puck design, I imagine they'll sell those separately.