I don't think there has been any official word by Google on this...however, I would think that the Nexus 4 will not get official updates to M. From the developer community (custom ROMs), that may be a different story.
Re: is Android 5.1 os end of nexus 4 os version updates???
By the time M is released, the N4 will be three years old. Google has been generous to support the phone this long by industry standards. I'd like to see an official M release on the Nexus 4, but I'm certainly not counting on one.