If my memory serves me right, they shouldn't be able to change the release date after today.
Per Steam guidelines, this appears to be true: Planned released dates cannot be changed within the 14-day window prior to the intended date.
This is so Steam can promote the game as "coming soon" and publicize it accordingly within their discovery system. A release only gets one chance at this. If Uberpie misses that planned release date (which can happen), it does not get the same kind of push as it would have had it released on time.
So it's not a guarantee, but Uberpie will have fucked up if they don't release it on time.