Electronista is reporting that the next generation Thunderbolt will reach 40 Gbps, though will have new connectors, and use up to half the power but still be able to charge 100 watts. It will support display port 1.2, PCI e 3, HDMI 2, and USB 3.
This would mean a much improved MacPro, though still not PCI e 3 x16 speed.