This website has a running tally of the whooper population.  The original flock had a bumper crop of chicks, bringing the total species population over 500:

Wood Buffalo NP (Alberta/NWT) / Aransas NWR (TX) flock: 237
Florida nonmigratory flock: 53
Wisconsin / Florida flock: 83
Total wild 373 birds
In captivity 145
Grand total 518

Not bad for a species that was down to just 21 birds for a couple years in the 1950's.