Official Numbers
Day 1a: 1,287
Day 1b: 1,545
Day 1c: 1,743
Day 1d: ???
There are currently 4,575 entrants who have played at this point. They are expecting another 1,600+ players on the final flight scheduled on Monday. That would bring the totals past 6,000 for this year's WSOP. It's not as many as the record setting main event from 2006, but it's more than 2005 when Joe Hachem won.
Here are the official number of entrants since 2000:
2006: 8,773
2005: 5,619
2004: 2,576
2003: 839
2002: 631
2001: 613
2000: 512