Tom's have a performance preview here: http://www.tomshardware.com/reviews/core-i7-4770k-haswell-performance,3461.html
They compare it to the 2700K, pretty similar to yours. It's a similar step from Sandy to Ivy again by the look of things, generally a pretty modest 7-10% increase at similar clocks. The integrated graphics takes another significant step forward, but that's irrelevant for you unless you're using quicksync. Also there's native USB3 & SATA 3 with the CPU (six of each I believe - don't quote me!) But again, if you have a high end motherboard you probably already have everything you need in those departments.
The big unknown at this stage is how's it going to overclock. I don't think that's question's going to be answered until numbers of people get their hands on retail chips and share their experiences. If I was you, I'd be waiting until a couple months after release to see the OC trends before upgrading.