The 90 day period for considering certain distribution options is extended to 180 days. If the plan doesn't mention the 90 day period, is the extention to the 180 day period an item that must be mentioned in a PPA amendment (yes I know it does not have to be amended now)?

I would include the 180 day period instead of the 90 day period, regardless of whether the plan deadline for amending the plan has arrived yet. Otherwise, you could risk confusion, resulting in an operational violation.