Here is my release estimate/guess:
From what I read in DBSTalk, Mark Lamutt has stated there is a bug "THE BUG" in the 921 that needs to be fixed prior to its release. Mark also said that the bug has been reproduced and is being fixed. So I am just checking
http://www.dishnetwork.com/content/customerCare/technical/software_versions/index.asp
every so often for an update to the 921 software. When it goes beyond L1.42, I suspect that the problem is fixed and the 921 will be released.