I'd think so (although some may wait awhile until the whole news/new-ness aspect of his making an announcement about it wears off). I hadn't even realized that this was something that was still kept hidden among professional athletes. I guess would have just assumed that it was something people knew off-camera (or mic or in public interviews) but didn't talk about because usually when people are talking about pro athletes they're talking about the sport, itself.
I don't really think there's going to be a big rush of people making any announcements about themselves, though. I'd guess it will be a kind of gradual thing (but not something so gradual that the majority of gay athletes will still be in the closet several years from now).
Someone on TV said something that I thought was nice, and that was that a lot of players have buddies who are gay, so their being supportive of Collins isn't at all a surprising thing.