It is settled law in the sense that the Court of Appeal, which is the superior/ultimate court in NSW, has ruled that that is the position. Jimmy is right, what was decided before is no longer relevant. If that case went before the Supreme Court now it is probable that the result would have been different, because of the Court of Appeal decision.
Yes your lawyer friend is right – there is no such thing as settled law to the extent that any principle/judgment can be challenged in a number of ways. It could be appealed to the High Court, or there may be another Court of Appeal decision that overrules some or all of what was said in the decision.
However – the courts below the Court of Appeal are bound by the decision, and have to follow the principles enunciated in it. How they interpret those principles is another question.
The “real lawyers” can’t tell you what will happen in any particular case because they never can – every case turns on its facts and how the law is interpreted as it applies to those facts. A lawyer can tell you what the law is and how they think the law will be applied, but that doesn’t mean that is what will happen.