It finally happened. The Xbox One has entered a new phase in life, the phase where Halo 3, Halo 3: ODST Campaign Edition (includes the campaign and co-op firefight), Halo 4, and Halo: Combat Evolved Anniversary have been ported to the Xbox One via backward compatibility and not through The Master Chief Collection.
It's important to note that this isn't The Master Chief Collection because while the collection includes Halo: Combat Evolved Anniversary, Halo 2: Anniversary, Halo 3, and Halo 4, it also includes some technical issues.
Today, Halo fans will be able to dive into Halo 3, Halo 3: ODST Campaign Edition, Halo 4, and Halo: Combat Evolved Anniversary via backward compatibility. These titles join Halo: Reach which went backward compatible in 2015.
The only thing Halo fans have left to hope for is that Microsoft remasters Halo 2: Anniversary for the Xbox One.