Not all of the current Rockin' effects were installed when the ride was refurbished. When people distinguish between Rockit Mountain (2006) and Rockin' Space Mountain (2007) they're really talking about two different versions entirely. When Rockit Mountain originally premiered, there were a LOT less effects than there are currently. It was certainly more tacky before. Between Rockit's closure and Rockin's debut, they added many more new effects and expensive lighting equipment. I've been on both versions multiple times (Rockit twice and Rockin' at least 6 times) and there were definitely differences between both of them.
As for Rockin' in 2008, it's been mentioned that if it does come back, it wouldn't be the RHCP again. Which, IMO, is a smart choice because they didn't work at all for me on Space. "Let It Out" was a lot more "rock" and gave the ride the oomph it needed to really be rockin'. The best part of the RHCP was the last 10 seconds when the soundtrack really kicked into high gear; unfortunately, that left you going "WTF?" the other 50 seconds.
I wouldn't expect to see it on Screamin' this year, either. Something tells me the ride will probably close sometime early next year for Midway Mania construction and/or a redressing of its queue.
EDIT: I just checked the Disneyland.com calendar, and there's no listing for a refurb of Space on those dates. When was the last time this info was checked??