Depends on your travel schedule next year. Main GM benefits are STE+ (aka lounge access for international travel), SKY boarding, and an earlier window for C+/F.
None of those scream worth $950 vs keeping FO with a big rollover next year unless you have a fair amount of international travel for the lounge or want a slightly higher chance for C+/F.
If you've already made up your mind that you want GM, taking the JFK - SFO upgrade is reasonable - at least you'll get D1 and lounge access out of it