I remember back in 1995, Cirrus was talking very big and touting themselves as the next $1 billion semiconductor company. Their stock went over $60 that Spring before ending the year around $20. It basically spent the next ten or so years declining all the way to $4 and that was before further losses during the 2008/2009 crash. On the good side, Jason Rhode was still toiling at UMD during that period.
We are all speculating but I'm sure both Apple and Cirrus are working hard to not to overly dependent on each other when at the same time they are in a hard embrace. They both know the rules of the market, I hope Cirrus has got parallel design teams churning out other products which can then replace with Apple's when and if they eventually divorce. In that case, IMO, they would see a dip for some time but should still hold on well.