Does anyone know what will happen to WatchKit 1 apps when Watch OS 2 comes out? (i.e. where the WatchKit extension runs on the phone and not the watch, uses shared app filesystem containers for storage, etc.) Will they continue to work, or will they stop working?
WatchKit 1 apps when WatchOS 2 comes out?
According to Apple's documentation, many (if not all) apps will have to be reworked to run on 2.0. Apple needs to develop a 1.0 compatibility mode for 2.0 before it's released, otherwise there will be a huge public outcry when people upgrade their Watches to 2.0 and find their favorite apps no longer work.
I suspect it will be the same as any other OS update.
Apps will run just as they did before, but need to be tested in case there are underlying API implementation changes that affect the behavior.
If you want to take advantage of WatchOS 2 features like native apps or complications, then apps will need to be recompiled against iOS 9.
Of course, the best way to get an answer to this is to test the individual app with an unchanged binary compiled for the released operating systems running on an iPhone with iOS 9 and WatchOS 2. This is always a good idea anyway, and one of the primary reasons beta operating system versions are provided to developers before being released to the public.