We'll see what they've done in a week or two. I wouldn't be surprised if its basically just a processor, chipset and graphics update of the existing model. You'd think that they would take the opportunity to make it a system that fills the many roles the platform is capable of though - especially now the Xserve is no more.
I am hoping for a strong update, but I don't know Apple's plans. The base machine is pretty bad for what it costs at this point, and I don't want to have to push it to a $4k+ purchase
Edit: ports, IO bandwidth, and ram tend to be bigger limiting factors for me than cpu much of the time. That's what I was getting at.