There will never be a stable point reached with infrastructure. There will always be changes in progress or being planned. There are also countless plans that end up being abandoned. But as long as technology is progressing and as long as people are moving in and out of cities there will be modifications to the train, airports, roads and bus services.
There are plans for a train station at waterloo. This will mean a very major renovation for the entire surrounding area, with the present public housing being removed. This line may continue through to another new station at McEvoy St, Alexandria or the Green Square station on the airport line. A connection at Green square might be convenient for airport transfers, but the plans are still not finalized. The earlier option for putting the new station at Sydney University has been dropped; waterloo looks to be the final choice.
The Parramatta to Epping rail link has long since been dropped (late 2012), but servicing the two suburbs with a light rail instead seems likely. The rail link out to Rouse Hill has been in discussion for over a decade without being implemented. A T-way bus system has been doing well in this area since 2007; perhaps this is sufficient.
There are two overlapping patterns with transport changes. One is new systems and modifications being implemented to work with the perceived needs of people. The other is people changing their habits to make the most out of the transport situation. This second trend occurs more than realize; people will tend to find the cheapest fare, or find the most convenient way to get around. There may be a period of breaking old habit for new ones, but people find what works for them. When the Opal train/bus cards were introduced people soon found out how to keep fares at a minimum, travelling off-peak, making the most of price caps, and taking advantage of very cheap Sunday travel. We know, but often forget, that it is the destination, other people, the business enterprise, or one of many other reasons that actually gets us travelling. We forget how convenient the transport actually is, and end up getting on with our lives once we find a reason way to get around.
Sydney airport Shuttle transfers are set up to provide the most convenient transport to and from the airport. Concentrate on you vacation of business trip, and keep travel time quick and pleasant with a private shuttle.