Given the extremely large amount of publicity and exposure this Open Call got and based on Anthony's recent comments about "being hosed", I still stand by my predictions of 40,000+ submissions. But I also think that less than 10,000 will make it past Christine.
Looks like I'm well over the mark at 22,222 but some others might have a close call (pretty much all from the first page):
MythusMage said 10,000
Psychotic Dreamer said 13,666 ...perhaps his neighbor's dog told him that number
Harlock went with 10,562 ...or 2 .... or a fish
KDLadage said 8000 to 12000 which probably means he's right but we don't allow area effect attacks for guesses
The Sigil comes in with 11,394.5 ...I'm truly concerned that WotC will ignore half-submissions; I've heard that some of their staff members were former vote-counters in Florida...
theRuinedOne is a dark horse with 18,000 but so far all we've heard is that the number of submissions exceeds 10,000 so I think tRO still has a shot.
Well, even though I overshot the mark at guessing 40,000 I still maintain that only 5000 will even be considered as viable world possibilities. and of those 5000, 3000 will be disqualified as being unworkable, copied licensed worlds, or just plain nuts. That leaves it down to 2000 actual worlds that have merit and 500-1000 of those will be duplicate ideas of other submissions that will likely get them both canned just because of the similarities. Now I am just hoping that my submission is part of that remaining 500-1000 that are serious candidates (but obviously I am not holding my breath).