Prices of hybrids in general should trend downward over time, just as the price of high end computer systems has done so. I remember when I was growing up, a "high end" computer system cost at least $5,000. That remained true for some time, but with the proliferation of home computers and efficiency gains in production, prices declined sharply. A "state of the art" computer can now be had for half the originally accepted $5,000 price tag, or less (I upgraded in January '06 and got mine for under $2,000, but I didn't need to purchase a new monitor.)
Also, while I haven't seen it corroborated anywhere, some think that the purchase price of hybrids will trend downward once the Federal Income Tax Credits for hybrids are phased out. The logic goes that the car manufacturers and dealers view the federal tax credit as a sort of built-in discount, so there's less incentive to adjust costs more in line with non-hybrid vehicles (which have their own host of purchasing incentives, like Ford's downpayment matching -- applies to everything but their hybrid models, etc.)
P.S. The Lexus hybrid,
Lexus Rx400h, is already available. As mentioned, it's one of the "performance hybrids" not one of the "fuel economy hybrids"... but it does get better fuel economy than anything else in its class of vehicle.