This should be part of the 4.1 that is going to be released on Monday, 23rd of December. I say “should” because people is struggling to bring all the changes together and release them before Christmas.
You are right that this took more time than expected. The fact is that many client developers were kept busy by the Android and iOS versions as well as by some other important fixes, so it seems that this feature did not get the attention it deserved.