I didn't notice much of a difference on the RX8 Fire over last year's RX8, but I didn't have last year's on hand to ski back to back, either. I would imagine that the ski, if any changes were made, is slightly improved, simply because tweaks are usually to fix small problems that become apparent over time, or to take advantage of new technology. Who knows, maybe it got worse instead, but I doubt it. I don't have an 07 left for demo, so I won't be able to do a back-to-back test anytime soon.
Not sure about the Race SC, but it seems that I heard it was similiar, if not the same ski, to the RX8. WC SC is a completely different ski, much beefier with a wood core; basically a masters SL or a freeskiing, high-end carver.