I’m surprised that you (and others) are not willing to accept the information that is already out. The things you are asking is the equivalent of ‘when will mythic cross realm be available’ or ‘when will the valor cap be removed’. That kind of stuff is never known in advance. What we do know is that initially it will be one item a week. Later it at some unknown date it will increase in frequency to serve as a catch up system for alts.
The information about the catalyst is out on sites like icy veins and wowhead and even today Blizzard have done a blue post.