Microsoft is allowing those who upgrade to the new Ultimate Game Pass membership for $1 to convert all of their Xbox Live Gold or Game Pass time (up to 36 months) to the Ultimate membership at a 1:1 conversion rate. (see photo) This will not be the case AFTER you upgrade to Ultimate. You can see post upgrade conversion rates here: xbox.com]
Ultimate Game Pass combines PC Game Pass, Console Game Pass, and XBOX Live Gold. If you are not a PC gamer, this will still come out to be cheaper than not upgrading to Ultimate.