So on looking I actually couldn’t find explicit mention of it, and believe I might be remembering a meeting I had with an Asana employee awhile back on a discovery meeting where they stated that it’s not going to change. Which is to say I don’t really have anything from staff that would support my claim that they have explicitly said they will never do it.
However, I will say that it is implicit that they never will. It’s a philosophy choice of theirs since the start - Why one assignee?. Notice at the very bottom left that’s an Asana publishing company. If you go to this thread Assign multiple assignees on one task and look for the posts from the employees they will state “they don’t see this feature coming any time soon” for multiple years in a row.
Apologies that I might have made a stronger statement that what I could back up with what Asana as posted online. Again though, short of having an explicit announcement, it’s been an extremely consistent view of theirs to state their reason is based on their core philosophy, and they have never hinted (that I could find when looking at this) that they plan to change that philosophy.