LGBTQ people want the freedom to live their lives without having to hide aspects of themselves and without having to face prejudice. That's why coming out is so important. When people come out, they say, "This is who I am. This is what I am like. Accept me for who I am." Coming out enables people to be confident in who and what they are.
The ultimate encouragement for a player to come out, would probably be that there were sufficient other gay peers for it not to be such an issue, or at least enough to be able to offer support. As it stands, that day seems a long way off. If the Premier League is to wait for its own Jason Collins, it may be waiting a very long time.