Thank you! That was very helpful and confirmed everything for me.
I suspect the new Base Cards will be almost identical to the old one. All the cards have undergone new artwork tweaks, which older players of the game may want, and they'll probably throw in the new Trash mat just to appease the public. It would be nice if they threw in the new Bane marker card, too.
There is no reason to include new Ruins, Shelters, or Heirlooms in the box because those are all expansion-specific. That being said, the selection criteria for Platinum/Colony is the same as Shelters, so if the former are included, the latter should be too, although I feel none of these actually need to be included. Similarly, Potions are extremely expansion-specific, so I see no reason why they should be included in the Base Cards set. I know why they were included originally – the entire set was envisioned as an alt-artwork set – but now that the Base Cards are is in all the Second / Revised Edition printings, that aspect is no longer needed.
I think the Base Cards should be released as a much smaller expansion and rebranded as the 5-6 player expansion. It should just include 20 Coppers, 30 Silver, 18 Gold, 20 Curses, 6 Estates, and 6 Provinces. That's exactly 100 cards. The Update Packs each contained 80 cards, so the boxes would be just about the same size. Just an idea.