There's an inexorable trend for sensors to increase in size and decrease in price.
A 24x36mm chunk of silicon wafer will always be a 24x36mm chunk of silicon wafer, and there's no real reason that I can see to expect the price of silicon to plummet. Yields will probably go up slightly, but CCDs aren't pushing the limits of feature size in the way that CPUs are, so I wouldn't expect that to have much of a price impact.
The general reason why digital devices keep plummeting in price is because advancing technology allows them to be made smaller, and smaller is cheaper. Fix the size of the device and you lose that advantage. You can still get "economies of scale" of course - up to a point, the cost of your product decreases if you can sell it to more people.
So, personally I don't expect to see an *enormous* reduction in DSLR prices - it'd be nice to be proved wrong tho' ;-)
S
