Smartthings is open to HomeKit compatibility in future models of the hub, but it requires a hardware piece the current model doesn’t have. this is one of the main reasons there are so few HomeKit compatible devices on the market right now. Even Philips had to put out a whole new version of their Hue hub to get compatibility.
So you might see it in the V3 for the hub, but it’s not in the V2.
If you’re looking for a home automation hub with HomeKit compatibility, right now your only choice is the Insteon, and then only the specific model with that hardware chip in it.
My guess is that it will be summer 2016 before there are really enough HomeKit-enabled devices to put together a full system, but who knows?