What I understood from my dealer when I got mine, was intially without pricing when they first came out many dealers were scared to place large orders for 5.7 because of gas prices, how much would it be. If it was $3,000.00 more, etc. When they found out it was $1,300.00 or so, all he said is I would have ordered them all with 5.7's. So now that everyone knows I bet pretty much all the orders are for 5.7's and that is putting a strain on supply.
On a side note.... Not confirmed and is from a dealer. I already own mine so I can't see him lying, but appartently the pricing for the 5.7 is going up minimum $1,000.00 for 08's. So all you guys waiting for 08's good luck, you may be in for a shock and have to settle for a 4.7... I can't see them pissing people off like that, but Toyota itself stated that the orders for 5.7's were not predicted..