I wonder if this isn't going to be seen as a mistake in the future. What if a faster map is discovered in 3 years that happens to not preserve order? This stuff is really hard to detect, so there's no going back on it.
That was likely weighed and I'm guessing the answer is that they would introduce a new type under collections, but that the new dictionary makes most sense for users while also currently being faster
In Python, they'd probably just make it a separate class, just like `OrderedDict` is/was. People who needed the performance would use it and everyone else would enjoy the convenience of ordering.