Technically, it can't carry a 5k signal as far as I can tell, which is where the goal post is right now.
USB-C supports DisplayPort 1.3, but the implementation on the rMB is only 1.2 (are there any DP 1.3 GPUs around yet?) - in any case, I doubt the rMB has the oomph to drive a 5k display anyway. When USB-C turns up on future higher-end Macs it may well have DP 1.3 capability.
Now I'm wondering if maybe we'll see them combine Thunderbolt and USB-C back into a single connector.
That would make a lot of sense. Presumably, a future USB-C+TB port could sense when a smart TB cable was connected and use some of all of its wires for TB signals. However, ISTR that the reason Intel dropped the USB connector for Thunderbolt was that the USB rightsholders wouldn't let them.
wait, so with a cable that's displayport on one end and usbc on the other you can just plug into a monitor? can you do that while also plugged into power - strange they wouldn't have a displayport and power adapter.
(1) Yes, (2) presumably - with a suitable adapter and (3) I'm wondering if the Apple USB-C VGA and HDMI adapters are just USB video adapters and don't actually make use of the DisplayPort mode of USB-C. They seem to have some odd limitations that don't tally with the rMB specs.
Since USB-C can support DP 1.3, it may become the preferred monitor connection mechanism over Thunderbolt
Well, TB 3 will support DP 1.3 but, if USB-C takes off, I can see USB-C inputs appearing on 3rd party displays fairly rapidly. In that case, an external display could be a display, USB hub, webcam, Ethernet port *and* charge your laptop over a single wire (the last one is a trick that TB can't do).
Normal USB didnt kill FireWire.
USB and Firewire didn't start off as direct competitors. USB replaced RS232, Centronics and ADB (and was in limbo for ages because of poor Windows support). Firewire 400 replaced external SCSI and was also adopted as the standard interface for digital video cameras - USB-1 simply wasn't up to either of those applications. Until USB3 came along, Firewire was still far superior to USB2 for connecting external drives etc. let alone professional audio/video applications. Even so, it stayed a niche market.
TB and USB3 are more direct competitors - USB3 isn't as fast as TB
but its faster than any single external drive, and faster than your internet connection. USB-C/3.1 is even closer to TB speeds - but I'm sure that when the real-world benchmarks roll in, TB will still win when it comes to driving superfast SSD RAID setups that can actually push 10+Gbps. If USB-C takes off in consumer PCs, USB-C devices will become cheap while TB devices stay at their present levels. You'll really, really have to need that performance edge to pay the premium for TB.
But USB cant do all the things thunderbolt does. Like PCI-E. The whole thing for external PCI-E Cards is a thunderbolt thing and no USB thing.
Not for long...
From Wikipedia on USB-C:
As of December 2014, Alt Mode implementations include DisplayPort 1.3 [35] and MHL 3.0;[34][36] other serial protocols like PCI Express and Base-T Ethernet are possible.