All Tau bits available are from new Warhammer 40k boxes.

The Tau are a young race isolated over thousands of years, which turned to good account the peace found in a cultural renaissance scientific and philosophical exceptional.
United by devotion to the Greater Good, castes who form the Tau Empire have joined forces with other races in the form of voluntary allegiance to the Supreme Good.
The Tau Empire following its expansion in establishing colonies on any world capable of harboring life.