I thought the relationship went the other way, that AS 3 was going to be standardised as ECMAScript 4? Not that it matters, Iām likely remembering incorrectly!
Standards are a two-way street, and we're probably both right from different points of view. (Especially, because AS 2 also had a number of the features proposed for ES 4, so even if AS 3 was "solely" inspired to be an implementation of the ES 4 standard, ES 4 itself took inspiration from AS 2.)