Though there are already hundreds of mods available.
Various mods for Starfield from Nexus Mods.

Todd "Sixteen Times the Detail" Howard of Bethesda fame, says that Starfield will receive official mod support in 2024. Howard spilled the Creation Kit beans in a recent chat with Famitsu.

While a firm release date wasn't given, it was suggested that when it does arrive it will come through the Creation Kit that is used for other Bethesda titles such as Fallout 4 and The Elder Scrolls V: Skyrim. Howard says that "you'll be able to do almost anything, just like in our previous games." Howard notes that Bethesda will "go all-in" on mod support.

Official mod support coming roughly a year after a game is released seems to be Bethesda's usual MO. 2015's Fallout 4's mod support began in 2016, while 2011's release of Skyrim (for the first time) eventually got mod support in 2012.

Even with this lack of official mod support, that sure as hell hasn't stopped there from being literally hundreds of mods released already. Just on alone there are already over 1,500 mods released. These released mods aren't those most comprehensive pieces of content by any stretch of the imagination, but they are out there. Some of the more popular mods currently in use include a DLSS mod, an improved inventory design, performance tweaks, and FOV adjustments.