Provided that the game structure and mod tools are similar to earlier games, we will probably start seeing mods within the first few days.

Given how previous Bethesda games have worked you'll get basic mods like texture replacers and the like for the first few days/weeks until modders figure out some of the differences between FO4's plugins and archives and Starfields then you'll see some more substantial but still basic mods using tools like xEdit until Bethesda releases the creation kit a few months down the line and people can make larger more substantial mods like you see for Skyrim. One prominent modder plans on having dlss modded in I think by release since you'll be able to get it early.

There were mods minutes after Skyrim's launch. Unless there's a drastic change in how the games are set up, there are a set of mods that already exist that will work right out of the box if you install them manually.

The game isn't even out yet and people are excited for mods that will fix bugs. JFC there's a reason AAA games these days launch incredibly broken

I think the modding landscape is different than in 2011 (in a good way). I feel like I saw mod support for Hogwarts Legacy on Vortex maybe 72 hours after the game was released.

My guess is that by the time the first official .1 patch is out, there will be a handful of QoL/fix mods.

The mods will come very quickly. I'm sure there will even be a few on launch day. They took a long time to release the creation kit for skyrim which made making mods much more difficult, but the community still put out a lot just using modding tools from previous games.

The amount of time it's going to take for mods will depend entirely on how similar it operates to previous games.

If experienced modders look at it and go "Oh, this is just like Skyrim..." or "Yeah, this bit from Fallout will work..." then modding should be pretty fast.

If it's more different than previous, it will take longer.

There's no real way to know until it actually comes out.

Probably post-release, but don’t quote me on that