Brief history:

• In 2004, the default $wgImageLimits configuration variable was introduced, affecting only the preview size on the File page. Going from a constant 800, to a user preference that defaults to 800x600. This included the 10_000x10_000 value (r5195, thx @hashar ref T36041#385938).
• In 2011, download links were added to the File-description page, based on $wgImageLimits (r83791, T4581, T8834). Several designs were considered, see mw:User:Bryan/Bug_2581.
• In 2012, the 10K value was removed (change 5678) per T36041: Image page provides links to image resolutions greater than those supported by image scalars.
• In 2012, the download links were removed from stock installs (i.e. wgGenerateThumbnailOnParse=true, transformVia404=false), because these would synchronously generate 7 thumbnails otherwise (change 8032).

The default remained as follows for a while (src)

$wgImageLimits = array(
	array( 320, 240 ),
	array( 640, 480 ),
	array( 800, 600 ),
	array( 1024, 768 ),
	array( 1280, 1024 )
);

• In 2021, 2048px was added to $wgImageLimits by yours truly. (change 680765, T106263)

	public const ImageLimits = [
		'default' => [
			[ 320, 240 ],
			[ 640, 480 ],
			[ 800, 600 ],
			[ 1024, 768 ],
			[ 1280, 1024 ],
			[ 2560, 2048 ],

This task was asking for 1440px and 1680px at a time where 1280px was the largest (10K was unavailable for most files because we don't upscale, and it was removed in 2012). We have added 2560x2048 which should satisfy the needs of 2008 "widescreen monitors".

However, it's now 20 years later, so is that still enough for modern displays? Back in 2008, I used a 17-inch PowerBook with a 1680×1050 display. Today, I currently use a 15-inch MacBook, but it's a HiDPI 2880×1864 screen.

Thanks to MediaWiki thumbnail steps (T414805), as of last year, the 2560px option was expanded to a 3840px file. You can browse File:Motorcyclist_in_Midtown_Manhattan on Wikimedia Commons as an example.

That size seems enough to close this task. Note that there is a bug in the interface causing the label to read "2560" while linking to the "3840px" file. Fixing the link text is T401668.