Yea this is a valid point, but since TB 1 and 2 carried DisplayPort signals, there's no technical reason why Apple had to limit TB displays to just TB ports (that I'm aware of... happy to be corrected). They should've just worked.

But these ports won't have that problem. Although to be honest, the new Macbook has a pure USB3 port and not TB3 :) So Macbook owners might still have that issue. Dammit Apple!

I'd imagine that Apple has learned from history that its proprietary & non-widespread (niche) connectors have not seen the type of industry-wide adoption that they would have liked to have seen (a la ADC, firewire, iPhone 1st gen, etc) regardless of technical merit. They have diverted from industry standards when the current off-the-shelf components did not necessarily meet their design desires/criteria.

I'm guessing that they found a pretty decent strategy when thunderbolt took on the mini-dp port and added thunderbolt to the mini-dp connector. Sure there's some confusion in plugging thunderbolt into a mini-dp port, but as Apple was concerned, they were not taking away any functionality, but merely just adding the thunderbolt feature to an existing port.

Apple's potential adoption of Thunderbolt using the Type-C connector would be a similar strategy to the mini-dp/thunderbolt strategy. This finally allows them to unify ports on their whole line up macbook/pro/iphone/ipad/atv/accessories/power/displays, which with their scale would probably translate to a pretty massive reduction in cost for maintaining inventory of the many assortments of ports and manufacturing.

Based on the direction they've taken with the new Macbook and this announcement, It's pretty obvious that this is the direction they would like to go with and lays out the foundation for the expansion of the retina iMac into a retina thunderbolt display.

I'd say it's definitely more of a feature than it is a regression. The world of consumers has shown that it's been able to cope with USB 1 -> 1.1 -> 2 -> 3, with very little pain. For most people it will be the Type-C connector running at speeds varying from 12Mbps, 480Mbps, 10Gbps, 40Gbps... If you have the higher speed, you can supper everything below it (kind of like 10G/40G ethernet). Mac's will probably be sold with 40Gb Type-C ports, iPhones with 480Mb Type-C ports, Retina displays with 40Gb Type-C ports, all with the consumer being none-the-wiser as to whether they are running in USB mode or Thunderbolt mode.