I know it is a new port and it seems a bit radical to make all ports the same type, Apple see USB-C as the replacement to USB-A connectors so would replace all USB-A anyway. Since TB3 also uses the connector and they want to upgrade the Thunderbolt ports then they will also have to use type-C connectors there.Well we've really only seen the chassis for the 13". 15" might have some extra I/O. Also it was just a prototype...
However, a Usb-c Dock will be straight money for you...
I still argue 4 usb-c is a bit excessive though. Even for the next 4-5 years from now.(the next redesign would be more suited for usb-c only IMO)
Other manufacturers, as is common with new USB generations, add the port as another port rather than a USB replacement. Apple, on the other hand, want to push the port to be the new standard and therefore can only do that by replacing all current USB-A ports with type-C ports as that would force customers into using the type-C port, and encourage manufacturers to make accessories. Other companies should then follow.