Very interesting thread. Have to agree with most of what has been said above. I believe that in the next 5 years there is going to be a fundamental change in GA with most of what we are operating today being too expensive to maintain any longer.
There are, however, some effects from this that will change the aviation scene at nearly all levels. With the gradual decline of piston engine charter there will be either a replacement of those types with turbine (or possibly diesel) powered aircraft (with a commensurate increase in cost) or the communities now being serviced with piston powered aircraft will cease to have aviation services.
The VLJs referred to by OZBUSDRIVER are really the B58/C310 replacements but you would be a fool to operate them over the same sector lengths. They really open up whole new markets, people who would never have previously thought about using charter but went business class. The manufacturers are advertising operating costs better than turbines (probably excluding capital costs) for much better performance.
Another consequence is that airlines will need to rethink their current entry requirments because the opportunity to get those sort of hours is going to be limited. Perhaps there will be a growth in cadet entry not like the current cadet schemes but more like Singapore Airlines where the airline trains its own from ab initio to RHS.
If that were to happen then the number of training schools would be rationalised. How many could afford to train up to and including jet experience?
Its going to be a brave new world out there in a few years time. The changes are going to be coming thick and fast and given the traditional reluctance to change in Australia the screams will be heard loud and clear.