Yes, Folke -IS- working on an updated release of his original book as we speak. I have been in very current continuing discussions with him now as he is running down lots of pertinent new information for inclusion in the next printing edition. As he has said to me recently, the new edition will both update the original, and importantly, add much new information on the Post-War guns. He was just very recently on a major trip to visit and collect more data in Europe/UK.
And no, I have no idea on the timeline, but I would guess at least a year from now.
Blake Stevens is still in the game, there is nothing definite that I am aware of as to him hanging up his printers smock in the immediate future. The problem with "trying to sell Collectors Grade Publications" is that it is REALLY a labor-of-love enterprise, and will be very hard to just hand over the reins to someone new.
That said, John's books are absolute must-have resources for all technical details. They really are the only current source for the original armorers details. Can't recommend them enough.....and I have a full shelf of them. ;-)
Vieles ist bekannt, dass ist nicht offenbart.