Thunderbolt is already fast, but for some it's not fast enough. Now there are strong rumours of the next, faster, version
For a lot of things, Thunderbolt 1.0 was easily fast enough. But now that the new Mac Pro is out, there's a real reason to want more. It's because the Mac Pro hasn't got any internal expansion slots. To compensate for this, it is positively festooned with Thunderbolt 2.0 ports, to which you can connected external PCIe bus extenders.
These work for a lot of expansion cards, but not for any that require a really high bus bandwidth. That's where Thunderbolt 3.0 (if that's what it's to be called) will help. But not for existing Mac Pro users, of course. We'll have to wait for a newer, upgraded, model for that.
We've seen rumours in Apple Insider that are based on an Intel presentation slide about a new Thunderbolt chipset, "Alpine Ridge".
In addition to a doubling of throughput to 40Mbit/s, you can expect to see a lower power consumption and an increase in Thunderbolt's ability to power external devices - up to 100 watts.
The proposed new specification calls for a new connector - but there will be adapters for older standard plugs and sockets.
We think this will happen. There are precedents for 40Gbit/s connections - there's a version of Ethernet that runs at that speed.