I can think of eight cards at most that would be suitable candidates for removal but apparently at least one of them (Farmland) is staying, so I tried to categorise them into tiers depending on how "safe" the existing cards were. I wonder if only eight cards are being removed as although there are already 26 cards in the set, it includes some blank cards, and I recall hearing something about 27 cards in new sets.
Probably going: Mandarin, Duchess, Cache, Noble Brigand, Farmland. Some of these have some interesting effects but are generally considered weak, and Noble Brigand is a bit tedious.
Likely removal: Develop, Ill-Gotten Gains, Silk Road. I'm particularly unsure about Silk Road leaving as no other card gives you points for Victory cards but as a certain number are being removed...
Uncertain: Oracle, Nomad Camp, Inn. I would have expected them to stay but it looks like even if those above are all going, at least one more would need to be removed. Oracle is a bit tedious and the other two have interesting/unique effects even if they aren't that strong.
Probably safe: Margrave, Tunnel, Trader, Cartographer. I do find Margrave an annoying attack but it offers quite a lot and enough similar attacks (Goons, Ghost Ship) have already been removed recently. I've always liked Trader, the additional reaction is an added benefit and Tunnel has a nice reaction too.
Safe: Border Village, Haggler, Crossroads, Scheme, Fool's Gold, Stables, Spice Merchant, Oasis, Jack, Embassy, Highway. I'd be stunned if any of these are removed.