We hate to be the bearer of bad tidings but yes, 'tis true. It was Eating Las Vegas (itself destined for the Great Doggy Bag in the Sky) co-author John Curtas who broke the story last June, when he revealed that Bellagio's popular Italian eatery would be closing within the year (May 2014, we believe), although as to the reasoning, he could offer only: "Still quite murky. The murk may go deep, even to the thick black oil that pumps through a casino exec’s cold, unbeating heart." John took the opportunity, via his blog, to offer up a personal eulogy to some of his favorite of the restaurant's signature dishes -- don't let the appalling pun put you off. (Note: This notorious carnivore is also a big fan of Circo's lamb chops, so go try as many of these suggestions as you can, while you can.)
There are rumors circulating that Osteria del Circo is being cannibalized, somewhat rudely (since it currently provides the venue's small-plate offerings), by neighboring Hyde nightclub, which evidently needs more space. Time will tell; for now, take heart in the fact that you may still enjoy the the Maccioni family's cuisine courtesy of Sirio at Aria, which Curtas describes in the 2013 edition of Eating Las Vegas as "the more exciting of the two" restaurants these days.