Double Layer DVD writing is coming
The first sets of drives that support dual layer are coming. Here are some with good reputations:
* BENQ DW822A.
* NEC ND-2510A
* Lite-on SOHW-832S.
Also some older drives can be firmware upgraded with the usual caveats as The firmware page :: View topic - The Double Layer Upgradability Thread explains.
Short story is the NEC ND-2500A has a 70% success rate in upgrade. The BENQ DW822A will have an official upgrade.