Er.. In my post I somehow I forgot that Victory cards are, well, cards. I meant any 3 actions or treasures.
Fishing Village being an exception, most 3$ cards won't get along with Museum as well as Silver would, either they are terminal and can't be spammed, or they are villages and won't like that Museums in deck makes it harder to line Villages up with Smithies. Oasis is going to be an exception, and Fishing Village, but in general, nonterminal Silver at 3-4$ is rare.
5$ cards replacing Gold is admittedly a problem though, as there are lots of nonterminal mighty well be Golds like Stables, Lab, Hunting Party and Highway, and so forth, and 5$ is a more accessible price point. Even so, most of those cards are cantrippy and get cranky when you damage your mean deck value with green cards. So I think we'd still see Copper - Silver - Gold as a favorite, or at the very least Copper X Gold or Copper Silver X.
IGG breaks dominion itself, that's not much of a talking point. Horse Traders would lead to HT/Silver/Copper which isn't far from the spirit of the card, at least.