Not sure on this but Google seems to suggest this is at least the 3rd petition on this topic. http://www.1911census.org.uk/petition.htm
mentions one such (in 2007?) which attracted 23,600 names. It was rejected by the UK government "in particular arguing that to release the information earlier would undermine public confidence in the privacy of information which people would be asked to provide in future censuses."
Personally, I do not agree with the proposal. The vast majority of us do not need
the 1921 to sort out our ancestors.
Sure, it would be nice to know exactly which street grandpa lived on in 1921, but I can find the full list from the electoral registers, not just 1921. It seems to me that most new information from the 1921 will be about more distant relatives, people who are not our ancestors but are
someone else's. As family historians we need to be mindful that others out there see our activities as unwarranted intrusion, and this enquiring into someone else's living ancestors, in flagrant disregard of the promises made at the time (that's how it will be presented), is risking our reputation for being careful of privacy. We should think of the nonsense about the SSDI in the USA, where access to later records has been curtailed despite all the logic being that the measures implemented will increase
identity theft. That sort of attitude will almost certainly come our way soon and asking the government to go back on its word (or what everyone thinks its word was) will stack the deck against us. For no good reason.