I don't expect a letter. I think that O used terms loosely, since in an earlier email he appeared to have indicated only shareholders of record, but no date given. Then he gave the date of Aug 1, 2017 which quashes the theory of only those who had shares in 2013 were getting letters, but then said beneficial.
I think the technically correct statement would have been to state shareholder of record as of Aug 1, 2017
Either way, who gets letters is about as important as the federal lawsuit, as we all know about it anyway or will find out through our brokers.