If I fill in the blanks, what do I do when Catalyst go in a different direction?
The same thing you would do with the hundreds of other plot ideas Shadowrun has had over the years that weren't immediately explained fully. To name a few:
--Church of the Dragon
--Dunkelzahn's death
--Anything to do with Nadja Daviar...basically ever
--The Hestaby/Lofwyr Tir Tairngire situation
--The Watergate Rift
--Aztechnology being secretly super evil
--Dragon egg clutches
--Elves and reincarnation
--Drakes
--the nature of spirits
Information on all of these were presented in sourcebooks first as teases, rumors, conflicting reports, etc., back in the good old days. If your group used them and later on printed material went in a different direction with it, you just used what you wanted and ignored the rest, or else you left it alone and gave it time to develop in official source material. This might be different somehow, but I don't see it.