Although 1.3 will be popular, I'm not sure that it will bring in quite the same amount of people that 1.0's release did. This doesn't mean that ESF isn't popular, it's just that people were holding on to see a huge change from 2.0a to beta 1.0. Heck, there was so much activity involving the release and 1.0-related issues that a separate forum section had to be made (called "Beta 1" if I remember correctly) to house all of the threads that were popping up. Even then, this wasn't enough - Cheeseman and Cucumba had all active moderators promoted (temporarily) to Super Moderator status to handle the huge influx of threads and spam. Suffice it to say that the forums were rather chaotic. I'm not sure if we'll see that much activity for 1.3's release. After a bit of time (a week, maybe), I'm sure there will be plenty of people playing 1.3, but I'm not sure that you'll get as many people here at once as there were on the evening 1.0 was released - people seem to browse the forums less frequently now and will like pop in at odd intervals, rather than all at once.
Either way - if you want to try to get over 519 people on at once, then I can imagine you have some PM's to send out. As it stands, I don't think that 519 people frequent here, so it may be a while before you get at least 520 responses.
EDIT - I retract my statement with regards to 1.0 being the big day of activity. This is the last day I post directly after waking up from a nap -_-