It's hard to speculate on a ballpark timeline, ALPA will need to provide that info. Here's a link to Arbitrator Association's roadmap. Pay particular attention to page 3, a typical timeline, and also page 12 (appendix) that contains some stats (in days) for each part of the process. Complex and larger cases have an extended timeline. And in our case a decision would likely contain an award north of 10 million dollars.
https://www.adr.org/aaa/ShowPDF?doc=ADRSTG_003838