They should be arriving within 1-2 months as Black Edition 32MB cache drives, in both 1.5TB and 2TB versions. I believe the 2TB would actually put WD ahead of Seagate assuming Seagate don't pull their finger out and produce one.
Personaly, the thing that keeps me from buying 2TB drives isn't even the low speed or the concern about reliability of a new product...it's the cost per GB. I think seagate can see this, and is working on a 2TB that is a bit more affordable (Although I am sure they would love to make the WD look bad by releasing a 2TB 7200RPM drive first)
The 2TB WDs are still falling sharply in price, they're now the same cost per GB that the 1TB drives were only 3-4 months ago, they just aren't quite the same cost per GB yet. Look in the right place and you can get a 2TB drive for £150-£155 now.