I'm very much in favor of this rename. To see why, just browse through the original pitch and see how many times participants in the thread were confused about the difference between "dictionary literals" and DictionaryLiteral. I recommend against turning that into a drinking game, on health grounds.
In that pitch, the alternative suggestion was to eliminate it. I think there's a clear place for a static dictionary-literal-expressible type that preserves order and allows duplicate keys. Mirror uses it for good reason, as it's a good way of enabling APIs that take key-value arguments where position matters and duplicates are allowed, and I've used it in similar places in other code in the past.