That's just because the rigger book tends to be the last core expansion, and in Rigger 3's place it was released twice—original version and Revised.
Anyway, there are 5E books on the docket until the end of 2017/early 2018 already. Books on the current to-do list won't even be written by the time Jason is planning Shadowrun's 2020 releases. So can we please dispense with the jokes already? It's not funny anymore.