Rob seemed pretty bullish that the league could continue without Fox, I'd imagine that the salary cap will drop significantly and a few teams might struggle. Apparently the Glory needed a 1 million dollar loan from the FFA to restart.
This article gives the A-League some certainty, according to Sage the A-League and the owners were not permitted to negotiate with other providers under the deal with FOX and FOX has also indicated they're open to continuing as the broadcaster, just under reduced terms.