Thunderbolt -> Triple Monitor Mac Mini?
Solution 1:
If you get the Mac Mini with the AMD graphics it can support three monitors.
From MacRumors
Mac mini (Mid 2011): Two Thunderbolt displays. Mac mini with AMD graphics can support a HDMI compatible device on its HDMI port when using two Thunderbolt displays.
Solution 2:
The limitation is not in the Thunderbolt, but in your graphic card.
I believe the third display will have a black screen if you don't have enough power from your graphic card.