There's well over a month until the game is released. Plenty of time to add in crossbows and their variants (silver, daedric, etc.).
I think you underestimate the amount of development time it takes to add a new weapon class to the game.
Graphics of the various different crossbows they might have.(Iron, Wood, Dwemer etc.)
Animations for the crossbow.
First person animations for the arms using the crossbow.
Third person animations for the body for the crossbow.
Adding an addition ammo type, called bolts, not just for one type of ammo, but maybe a few different type. (Iron, Silver, Steel, etc.)
Distributing the ammo types throughout the world in a balanced way.
Distributing the Crossbows themselves in a balanced way.
They would have to make decisions about how powerful they are. How fast they load. How far they go. If they have an special properties. Etc.
Perhaps making a few unique crossbows like they did with the other type of weapons. (they could leave it out)
Just integrating a whole new weapon type into the world during a phase of development that should only include bug squashing is unrealistic. I think in general that you underestimate how long these things take to do.