One other possibility is of course to make an "addendum" version book,
which completes the 2nd edition instead of replacing it. Did anyone
think about that?
*sigh* Yes, that's the backup plan. If we complete a draft of TKD3ed and the publisher doesn't want it, we discussed ripping out the "new" parts as a separate book. That's undesirable because (1) more work, and (2) you need two books instead of one for a description of the complete grammar. (Technically, you'd still need KGT as well, but the new TKD will refer to KGT in, e.g., section 4.2.8 {-neS}, so that you could *look things up* in TKD and be sure that it didn't miss anything.)