The Dreadclaw has not been available for a bit now, and it now appears that it is not coming back. A replacement in the works and will be released later this year. Here is the latest of responses from Forgeworld.
A huge thanks to Matt for sharing this with us on Faeit 212
The Chaos Dreadclaw model has been discontinued and it will not be coming back. We have been working on a new larger model that we showed at our Horus Heresy Weekender and this will be released later this year.