There were hints pointing toward that, but it looks like we'll be able to dual wield some tools in 1.9.

Quoting the Dinnerbone: "The way I want dual wielding to work is that it uses the right click action of your off-hand item if your main-hand doesn't have its own. For example; if you have a pickaxe in your main hand and a torch in your other hand, right click places the torch."

This might make digging tunnels and mines a touch easier, and I'm looking forward to try it out!

Probably. That first image does say that the sword no longer has a "use" action in 1.9, which is currently set to block attacks. I'm guessing that the shield, on the secondary arm, will take over that role. The end result is that blocking will work exactly as it does now, except that it'll require having a shield equipped!