Apple doesn't have to make it expire. It's like forced obsolescence. I believe most users using jailbroken iOS 6 and are actively avoiding iOS 7 have installed the patch via Cydia; or others just aren't logging into their banks at airports regardless.
For proper security, it must expire. As dictated by the IEEE and even the most basic international encryption laws, every SSL certificate must have an expiration date within the certificate. The purpose for this is that no key can be guaranteed forever and it must at one point in the future be revoked by expiration and no longer trusted as it has the chance of being compromised. Unless Apple no longer wants to maintain complacency with the basics of SSL encryption, it must and will expire. To think this is planned obsolescence is just foolish and of poor overall judgement.
There's so much more at stake than logging into ones bank account at an airport with the SSL goto fail bug. Any SSL data, be it email, iMessage, or web pages, can be intercepted and decrypted. It doesn't have to be done at an airport or other public wireless network. The data can be intercepted and decrypted by a man-in-the-middle attack, within the ISP, where the ISP connects to the internet backbone, where the target server is located, or even out of the cellular data network by way of spoofing a cellular base station. Nearly every hop along the way is a weak point where the data can be intercepted and decrypted.
