This is correct.
The 72-500 name has been introduced to have a marketing commonality with the 42-500.
The ATR 42 were ATR42-200 (never entered service lack of power), -300 (upgraded to -320 for hot & high), -400 (4 scimitar blades) and -500 (more power 6 blades). The next series will be the -600 in 2011.
The ATR 72 the series -101, -102, -201, -202, -210PEQ, -212 and -212A
On the 72 up to the 210 it was a PW124B then it became a PW127, originally the series on the 72 where depending on the doors configurations and also the MTOW.