Yes, Storm in winter, Victory in summer. However, Victory are more popular overall, hard to escape it. People are generally more skewed towards soccer than rugby league (a lot of racial reasoning behind that), and as a result, general interest would be in the favour of the Victory. But, the Storm do enjoy their fair share of popularity.
And no, Season 4 begins in August, and the stadium won't be ready by then. But should be ready for first game of Champions League, and perhaps matches prior to that; not sure how they've contracted it.