This is what I am thinking too. The money is not a big deal so it seems like a no brainer to join, assuming we have a decent case. I have been doing some research on that right now - it seems historically mandamus claims against USCIS on AoS were typically filed after 18-24 months, as before that the agency could argue that it's not an unreasonable delay. IANAL, but given the super long processing times posted on their website for 485s and the fact that the GC numbers expire at the end of September, I am thinking there is a somewhat reasonable case that delays - even if arguably reasonable processing time at 11 months - cause irreparable harm. And I think maybe it could be shown that these delays could have been anticipated way in advance as it was clear there would be huge FB spillover.