Nintendo seem to be a little hit and miss on updating the Nintendo Switch Online games but just now, they've announced what we can expect for this month:

SNES

  • Donkey Kong Country 3: Dixie Kong's Double Trouble
  • The Ignition Factor
  • Super Valis IV
  • Tuff Enuff

NES

  • Nightshade

These games will all be available to play from December 18.

For the Japanese Nintendo Switch Online games (which can be accessed via a Japanese account), in lieu of Super Valis IV and Tuff Enuff on SNES, it will receive Kunio-kun no Dodge Ball da yo: Zenin Shūgo and Sugoi Hebereke. For NES, in lieu of Nightshade, it will receive Smash Ping Pong.