it is indeed a bit worrying. one possible reason why there may not be a huge drain on superleague is the already large pool of talent at the NRL clubs both in the first team squads and reserve grade (remember the holden cup is of a decent standard). yes they may pick off a few of our best players but may not want to sign players just to stick in reserve grade - a player who looks great in superleague is not always so hot in the nrl (hardaker, joe burgess, ben crooks et al).
i'm not sure whether a salary cap raise over here would solve anything, as we would never be able to compete on those terms with the NRL - it would bankrupt the game.
One possible idea may be to look at some sort of dual reg where teams link up and swap players, that way if we were to lose a few superleague players there might be a good up and coming aussie to take their place, though i'm not sure this would solve anything - just putting the idea out there
perhaps if mr wood and his cronies had been prepared to negotiate a better TV deal for the game a couple of years ago rather than take the initial offer and spent more effort in getting top sponsors on board we would be in a better negotiating position.