I would be surprised and annoyed if it were on the Halo Channel. That was just invasive and difficult to back out of. Personally I’m hoping it will open a YouTube link in browser and just show there although that wouldn’t be very nice looking.
So yeah, no clue how that will work but there are plenty of options on the table.
I'm pretty sure the reason they removed them was to reduce the file size, since the terminals add up to a few hours of hd video. But that was really only a concern because the original Xbox one only had 500gb of storage, and these days it shouldn't be as much of an issue on either Xbox or PC. They should just give people the option to download them.
I would truly prefer that they be integrated into the game like how it was done fore Combat Evolved Anniversary on the Xbox 360 (activate terminal -> play video). This would require the videos to be included in the files, thus making the file size larger. As to how much larger, I don't know. Spartan Jack 17 mentioned an option- that could be solid. Maybe in the Steam DLC tab or something.
It's a PC game dangit, we can handle the file sizes quite easily, considering just how huge future titles like Cyberpunk 2077 is apparently going to be, it's about time people upgrade to multiple TB-sized harddrives, they're not that expensive anymore.