If the entries are to be believed, then they confirm an increase in the pixel density from around 226 PPI on last year’s MacBook Pro models to 250 PPI.
It seems that these resolutions are indeed for the upcoming 2021 models of the 14-in and 16-in MacBook Pro, based on the resolutions themselves and their relationships with each other. A couple of new entries in a list of display resolutions in the System Information app show “3456 x 2234 Retina” and “3024 x 1964 Retina”, and neither of them match the resolutions of the displays on any current or past Apple product (via: MacRumors).