So if I set up a social recovery option, and then AirGap wallet with all its services ceases to exist 5-10 years from now, how can I regain access to my funds if the scheme doesn't work with other hardware/software wallets?
The code of our apps is completely open source and the part of the social recovery is only a few lines of code. I would recommend that you use an old deployed version of the app (eg. an APK from GitHub). You could also run the project yourself, or someone could build a standalone version of the recovery feature.
If you adopt the SSKR standard at one point in the future, does it affect all previously configured social recovery setups? Those created before your adoption of SSKR or whatever other model you decide to go for?
SSKR is a completely separate standard, so it is not compatible with our implementation. Once we add SSKR, the generation part will be replaced completely, so going forward it will only be possible to create SSKR shares. But our apps will always support recovery of "old" social recovery setups, we'll never remove that.