Here are some changes we expect to see:
- The Mac mini will use the new Mini DisplayPort that was recently showcased on the Macbook line. This will save considerable port real estate on the back of the Mac mini.
- The Mac mini will join all other Macs in being able to address 4GB of RAM. Currently, they are officially sold with up to 2GB of RAM, but can also support 3GB of RAM. (Though the latter configuration loses the minor dual channel benefits.)
- Like the new Macbook, the Mac mini optical drive will be changed to a SATA connection. (It is currently a standard ATA/IDE cable.) This will obviously increase performance. But this change offers even more benefit for those who use the Mac mini as a server. (I have hundreds of Mac mini servers in here that have never once used their optical drive.) In ordering a Mac mini from Apple, there will be an option to have two SATA HDDs and eliminating the optical all together. With the new Remote Disc introduced with the Macbook Air, this option will be tempting for many.
In this list above, we have 100% confirmed two of these upgrades. The other is just a 99% educated guess.