for Apple, mac mini has been the "entry level" mac, just cheap enough to entice PC users to move over to Mac.
if they release a new cheaper entry level iMac (there has been a rumour about that), I don't think they'll update the mac mini. Most of the people waiting for performance boost from the next mac mini, should understand that, though the mac mini server is fairly powerful and many companies do use them as servers, mac minis are not supposed to be as powerful as iMac. if it was, why would you buy an iMac over mac mini? keep in mind that most people already have a monitor and USB keyboard / mouse. honestly, I thought it was very generous of Apple to include Quad Core in mac mini. they risked losing lots of potential iMac buyers.
and now that they have a new Mac Pro for those who need desktop mac, I'm losing my hope of getting the next generation of mac mini. if you need something in between, there are slew of MBAs and MBPs.
Don't get me wrong, I want to upgrade my setup to a new mac mini too!