Will there be a good market for this?
I don't think so.
It is a question of numbers. There are far fewer transgender athletes in the classic male and female categories. So I wouldn't mind betting on transgender sports, but I doubt there are enough of them in some sports to make them competitive.
Take football, for example. There aren't enough trans people to set up a football league in any country, let alone a top level one, let alone one that can compete in terms of interest with the UEFA Champions League. Or the major national leagues.
In individual sports there may be a little more scope for interest, though.
