The announcements allow the forum community the opportunity to collectively assess the new upgrades and pilot abilities and analyze them for game turning/breaking combos or unintentional rules interactions. We are the third level of analysis:
1: Designers use basic mock ups with rough upgrade cards to test ideas.
2: Playtesters get a couple of versions to test and play with and to comment on.
3: Forum looks at final product and nit picks any issues it sees and computes all the different variables looking for new and weird card/pilot combos. Cards can be changed before final printing or at least FAQ'd shortly after product is released.
It also give us the benefit of anticipation for when it comes out. Something to look forward to.
I have not forgotten about Rebel aces. I have planned out space for two aces contents when I upgraded my storage a couple of months ago. If that came out willy nilly without any beforehand info, I would have to scramble every couple of months to find storage for what I was going to add to my ever expanding collection.
I think FFG gets their analysis from events and tournaments (such as GenCon) more than they do from a bunch of anonymous people posting on the forums (trust me, that's a good thing).
The forums are more for the players then for the staff, it gives us a place to talk about X-wing and for those competitive people that do go to those events can share lists that are competitive and try them out for attending FFG staff to see and analyze.