I am pretty sure they'll evaluate their options once the game is fully restored up to its condition before shutdown. They've added the old Vanilla POTCO skybox, which was a very nice addition and looks nicer than the slightly simpler one from later on. I prefer a focus on optimization over graphics for now.
If the graphics are ever improved I'd like to see it be more quality of life/immersion changes as opposed to art style changes. Stuff like improved render distances, more distant scenery, sun beams, shadow map increases, and character model proportion smoothing (characters look a bit jagged and not even from multiple angles) would be stuff I would consider.
If significant graphical overhauls were considered then I would add an option to use the old graphical style. I love the base style and aesthetic of Potco, and would like to see it remain as an option in TLOPO.
But ultimately they need to complete the game restoration and optimization first, which is the ultimate goal of the project in the first place.