With the new line up of Mac Minis we can have up to 16 GB of RAM, and 3.0 GHz CPU, and therefore they can act as a server. But why did Apple just drop the 'Server' keyword from the Mac Mini category?
They haven't announced a Server version, it may come later.
Only Apple can know that.
The 'Server' version was not the same as the regular version, it had 2 HDs, no optical drive & had OS X Server installed, rather than the desktop OS.
For all practical purposes, the "Server" configuration is identical to its non-server contemporary, but ships with dual hard drives and a pre-installed copy of OS X Server for Mountain Lion.
Apple has dropped server from its lineup.