TC devs are hard at work with perfecting Streaming Swaps and it's already supported by TC nodes.
Streaming Swaps enables traders to split their swaps into several smaller swaps over time, allowing arbers to rebalance the pools between swaps. This can make a huge difference when it comes to how much slippage big swaps are subject to.
As ShapeShift is already running ThorChain in the backend, I think it should be a no-brainer that ShapeShift should be ready to support streaming swaps when it's enabled :D