Well, a few things worth noting:
1) According to the original post ('cause I haven't seen this quoted elsewhere up to this stage), Ponting said "We're going to come up against some small grounds in the WC, so the consideration of batting second in odi cricket is something to think about,". It's not a pledge to bat second every match, just a comment that he may be more willing to do so than he has been (up to this point, from my memory, he's shown an overwhelming preference to bat first upon winning the toss). Doesn't seem that ridiculous a comment.
2) I really don't think the attitude in the Aussie camp would be "hey guys, seeing as I'm planning to bat second if we win the toss, we can not bother thinking much about what we've been getting wrong attempting to defend 300+ totals. Does anybody?
3) I'm not presuming it's necessarily a choice between setting 300+ ourselves or chasing 300+ down. Part of what I wonder about is whether this is simply a mental thing rather than an issue of skill - so it's quite plausible that if we were to bowl first, we may well roll other sides for moderate totals on grounds that are conducive to very high scoring. Further to this, I don't really think we're absolutely beholden to the toss. Yes, we've shown a definite weakness in this context in that we've had a number of high scores we've been unsuccessful in defending, but it's not like we lose every game in that context, and I would think that, considering we tend to win at a very healthy percentage, we're certainly capable of winning games defending high to quite high totals.
4) I don't really think we're at that much risk of being sent in by all opposition teams in the light of Ponting's comments. Most teams in friendly batting conditions would probably still prefer to bat first and set a target, I would think, though one or two might be more amenable to chasing (ie the WI) in general.