Forgive me for being slow on the uptake. It has been so long since Library and Archives Canada took possession of the 1921 Census that I had stopped looking for updates. I've been behind in reading other blogs. Only today did the Ottawa Citizen publish an article saying that the census was finally been made public late last week. Ancestry.ca is making public the digital images of the 1921 Canadian Census. It has not yet been indexed by name. I understand that it is possible to search by location, if you have a good idea of where your people lived in 1921, and you're willing to scroll for a while. I will give it a try now.
For an excellent compilation of information and perspectives on the census release, please go to the Genealogy Canada blog here.