This seems like the strongest indicator thus far that 2* and/or Promo card trading will eventually be made available. (Leak, not confirmed)

In a past announcement they said “We are planning to gradually expand the selection of cards that are able to be traded” which was a bit vague, leaving room for the possibility that they were referring to gradually expanding to include future booster packs in trading. Now seeing the phrasing “expand the range of cards,” it seems more likely that they are referring to making other rarities available for trading.