I think we should remember that a computerized DVC booking system is already in place - MS uses it every time we call to make a reservation.
Perhaps it needs to be more advanced - or not. I can't say for sure as I certainly have no experience with the code/expectations/results of the current system - but certainly the 'rules' were taken into consideration when that system was built.
What is needed is the customer interface that needs to be bolted on - along with enough infrastructure (server/network) capacity on the back-end to handle expected volume.
We should also remember that Disney is really pushing DVC sales and an online booking system would be a nice feature to tout.
My humble opinion is that going forward, prospective DVC buyers are younger, more technology savvy and very aware of the multiple choices they have when it comes to plunking down vacation dollars.
I think Disney is not blind to advances competitors are making and would really, really like to not be the last major timeshare to have online booking.
I think it will happen sooner rather than later...but don't ask me to define sooner vs. later.