.bet domain names are currently at the pending release stage. Even if you pre-register names, you are not guaranteed to get them. Personally I would not register any of these names as I think they are likely to have trademark issues. In addition to that, betting companies tend to use names that are not linked to one sport. aflbet.com is for sale and aflbet.com.au doesn't resolve, so I think selling afl.bet would be a long shot