UPDATE: Microsoft has confirmed that Halo 4 launches worldwide on 6th November.
"We are beginning a new saga with Halo 4 and embarking on a journey that will encompass the next decade of Halo games and experiences," commented Microsoft Studios VP Phil Spencer.
"Millions of fans worldwide have been eagerly awaiting the opportunity to step back into the boots of Master Chief, and, with Halo 4 leading the charge, we're confident 2012 will be the most successful year in Xbox history."
UPDATE: Halo 4 will release on Tuesday 6th November, according to a new report.
The Verge claims developer 343 Industries and publisher Microsoft will announce the date before noon ET today - 5pm UK time.
The announcement may be linked to US TV chat show Late Night with Jimmy Fallon. A number of tweets from Microsoft staff told fans to expect Halo 4 news today and linked it to Conan O'Brien.
A tweet by Alison Stroll, senior producer at 343 Industries working on Halo, said: "A little birdy (or was it Andy?) told us @TeamCoco†will have some big Halo 4 news tomorrow. Stay tuned!†#incoming†#wakeupjon"
And, from Major Nelson: "Look for†#Halo4†news on the way in the next 24 hours. Hint:†@TeamCoco†plays a part!"