Here are 2 different and partially conflicting answers from Apple...
"... 1. systems engineer..: Spec’s say that it should… probably won’t be chaining but rather 5K in one port. USB-C -> Thunderbolt Adapter in another port...."
2. "One of my other coworkers said the only thing he could foresee potentially being necessary is closing the lid on the MacBook Pro in order to use two external screens, but he still thinks it should be able to drive two displays. I don’t think we can fully know without actually trying it, which is pretty aggravating. As soon as we get the 5k in store I’m going to try this out, but there’s no word on when we might get them in..."
Any other thoughts? Anyone try this on their new 13" 4-port MBP yet? Does anyone think #1 will work? The previous post by glindon suggests that this is a GPU issue, not a port issue.