Apple didn't break anything. They're jjust doing one of their regular IOS upgrades. They are warning us that BIAB will not be compatible when they do that and therefore PG Music needs to being it into compliance.
"Will not be compatible" and "will not support" can mean 2 different things. Did someone at Apple say in these words "BIAB will no longer run on IOS" are they just not going to make updates with BIAB in mind?
This reminds me of when Microsoft said "We will no longer support XP" and 75% of the world started posting message like "XP won't work anymore!" All that meant in that case is that there would be no further updates for it.
I don't use IOS so this does not apply to me, but I am curious what they actually said because those 2 quoted phrases above do not necessarily mean the same thing. PG will fix it once they see it. Think of it in the same way I saw people scream at Norton Anti-Virus because Norton didn't put out a patch to keep people from initially getting a virus. Well, until they see the virus, how can they do anything to prevent it? PG needs to see what doesn't play well before they can fix it. And they will.
In the meantime, if you really have a potential loss of work, I would dump your songs out to MP3 as a backup and play them as MP3s on a tablet or laptop. At least you can do a gig that way.