While third-party dongles are available, the good news is that if you'd rather not pay for something unofficial, Apple has extended its MFi program where it will now cover third-party Lightning to 3.5mm cables, assuming that the manufacturers are able to meet the specifications laid out by Apple.
The development follows yesterday's news that Apple is revamping the logos used on MFi products.
While it's possible some MFi accessories could use the USB-C port instead of Apple's Lightning connector or micro-USB, the new specs are not necessarily an indication Apple has plans to move away from Lightning. Apple does offer a fast 29W USB-C Power Adapter that will load your iPhone to 50% in 30 minutes flat, but that one will cost you $49 extra. This means that MFi-certified accessory companies that sell controllers, battery packs and even speakers, can now feature USB-C charging, while also maintaining Apple's seal of MFi approval. That is one of the reasons Apple has added specs for other non proprietary connectors in the past such as the Ultra Accessory Connector for headphone makers previous year. They can also use the USB port on their Mac with the same cable to charge their Apple device.
As the industry slowly plods towards transitioning to USB-C - in Apple's case, at least in terms of laptops - tiny shifts like this are important as the port technology progressively becomes more popular.
Up until now it was possible to use adapters as a workaround to not having this cable. The new cable would improve the user experience from an audio perspective and add more durability to the entire product.