Yeah, I think the answer to your question is "no, they cannot". At this point, they probably have a cogent idea when it'll go experimental, but given the scope and depth of the changes, determining when it will be ready for Early Access requires more oracular precognition than any of us are blessed with.
Even guessing when it'll be definitely ready for experimental is tough, because if Jace finds a serious bug 30 minutes before release, it won't release. That's unlikely, because finding a bug requires work and that doesn't sound like something /u/JaceAtCoffeeStain would do, but anything is possible.