If the casing is changed, then I don’t believe the 3.5 Jack will exist. It’s also a gateway for Apple to encourage the AirPods as well. Which is not to say the 3.5 mm Jack is not appreciated, but the AirPods are an excellent device for a Bluetooth alternative.
I'd use AirPods even if my iPhone 8 Plus had a headphone jack as I find them so much more convenient.
IMO the dual-goals of the iPhone SE are appeasing Apple customers who prefer the smaller form factor and appeasing Apple beancounters by leveraging existing industrial design and production capacity. As such, I expect the new phone to continue to be called the iPhone SE and to look identical to it's predecessor with an A10 Fusion CPU and iPhone 7-level cameras.