My guess is that Fox sees a new Australian entry to HAL as likely to bring more revenue to them than keeping Nix in. But these of course are not the only alternatives. Adding two more financially viable Australian mainland sides to HAL would be a win-win situation, without us being seen as dispensable.
I do not honestly see our football as likely to prosper (at least short-term) without taking part in HAL. But I do not see HAL as interested in ditching us unless FFA is running into some new headwind at AFC, which I have not heard about so far.