I think his $5k estimate is much stronger than his $20k estimate. An Apple Editions is not a Patek Phillippe. There is a dramatically different replacement cycle which means that any attempt to cut and paste lux strategies is going to either fail entirely, or narrow the market so thoroughly as to be indistinguishable from failure.
I'd also expect one of two things to surface here - either the watch forever remains so incredibly lightweight in what it can do without the phone that upgrades are less necessary, or there will be an upgrade program for the expensive watches.
If there's an upgrade program (i.e. replace the S1 with S2/3/4 and upgrade the battery yearly) then I'd actually expect these gen1 edition watches to become quite the collector's items - especially a few years from now when there are only a handful of gen1s around but far more gen2/3/4 watches.