Update: It looks like the Xbox.com posting hinting at Halo 3: ODST's digital release on Xbox One is placeholder. The official Halo twitter account tweeted the following.

A placeholder release date for the ODST campaign for Halo: The Master Chief Collection was inadvertently listed on the Xbox Store. (1/2)

— Halo (@Halo) May 27, 2015

We continue final testing and will make an official announcement once our release date is determined, and apologize for any confusion. (2/2)

— Halo (@Halo) May 27, 2015

Original story posted May 26, 2015 at 07:31 PM:

According to its listing on the Xbox.com marketplace, Halo 3: ODST remastered for Xbox One is only a few days away.

You can find the listing here, as well as a screenshot of listing above. It shows that the game will be available on Friday May, 29 and will be 8.1 GB to download.

Following the botched online multiplayer launch of Halo: The Master Chief Collection, 343 promised it would give the Halo 3 follow-up campaign, ODST, the same remaster treatment and make it available for free to Master Chief Collection owners. We've known the game wouldn't be too far off, and even that it would release in May, but this is the first hint of a solid release date.

[Source: Xbox.com]

Our Take
This could certainly be a mistake or an inaccurate release date as it doesn't appear 343 has confirmed the date anywhere else, but it has said the game would be available in May and considering the last day of May is this coming Saturday, a Friday release seems like a pretty solid bet.