They actually have, just recently, though.
Blizzard says Diablo 4’s respec costs “are final”
The article it’s referencing was posted 8 days ago.
But the relevant part in the article that actually promotes more posts on the topic is this part here:
He added, “We’ll always be looking at data, and we’ll be considering the feedback that we’ll be getting post-launch. We want players to get a chance to actually experience the system and see what it actually feels like rather than seeing screenshots that might seem a little absorbent initially. And then we’ll take a look then.”
So after launch, expect to see more posts about respec costs especially from the people who want free respec costs, period.
(edit) Idk if dev interviews = blue text, though. If anything, it’s more authoritative than blue text, right?