Essentially they are reworking the character face system to add more variety in selectable face shapes (and likely skin tones) and to make various other options (face paint/markings) that are automatically adapted to each face type rather than having to be redrawn for each permutation. The new system will apparently make it easier for them to add new appearance options in the future, which they have said they plan to do. However it also means that some players will notice slight differences in the appearance of their current Guardians when the changes go live. Given these two facts it seems entirely reasonable to expect that players will at least be given the option to rework their Guardians’ appearances at some future date. (΄◉◞౪◟◉｀)