"In 2015, when the iPhone 6S and 6S Plus were announced, Apple also introduced 3D Touch. 3D Touch uses a Taptic Engine with haptic feedback, which allows the device to sense the pressure of a touch, thereby triggering specific actions. For example, pressing hard on an icon will enable us to quickly open an action menu." - Clayton, C. (January 2018). Learn iOS 11 Programming with Swift 4 - Second Edition.
"3D Touch is basically a technology that adds another dimension (hence the name) to the tapping mechanism that you find in every iOS device. Traditionally, a user could perform the following actions on an iOS device’s screen using her fingers:
With the availability of 3D Touch on a device, a new vector that registers the strength of a touch on the screen is added to the formula, allowing the user to keep her finger on the screen and apply more pressure until an action (application specified) is performed. 3D Touch simply allows the iOS device to have access to how hard the user is pressing her finger on the screen, and this opens the door for a whole new set of applications." - Nahavandipoor, V. (2017). iOS 11 Swift Programming Cookbook.
"3D Touch works because the iPhone’s screen is pressure sensitive. You can press on the display, and the harder you press the more “happens.” Haptic Touch screens, like on the iPhone XR, don’t have this pressure sensitivity. Instead, Haptic Touch appears to be just a new name for our old friend, the long press.
seems like Haptic Touch can do most of what 3D Touch does already. In iOS 12, a new trackpad mode was added, one that works with every iPhone and iPad. Trackpad mode lets you press hard to turn the iPhone’s keyboard into a trackpad, which in turn lets you control the cursor in the text above. The new mode lets you do the same by long-pressing the keyboard’s space bar. I’m almost certain that this feature will get a Haptic Touch vibration in the iPhone XR." - Sorrel,C. (September 2018). What’s the difference between 3-D Touch and Haptic Touch?
"It’s important to remember that not all devices have a Taptic Engine; in the devices that don’t, the feedback simply won’t be played. This means that you mustn’t rely on tactile feedback (...) it should be used to underline effects that are already visually or aurally present." - Buttfield-Addison, P., Manning, J. (October 2018). iOS Swift Game Development Cookbook, 3rd Edition.
"Considering they removed 3D Touch from the device to cut manufacturing costs and to give us the new "Liquid Retina" display, we don't expect any real pressure sensitivity to be associated with Haptic Touch." - Peterson, J. (September 2018). All the 3D Touch Actions You'll Lose by Switching to the iPhone XR with 'Haptic Touch'.
At this stage it’s somewhat unclear how many of the functions supported by Apple and 3rd party apps on 3D Touch can and/or will be supported on Haptic Touch.
With this, what's happening now with 3D touch seems similar to what happened with Force touch back in 2015. The Haptic touch meaning is more specific describing the set of possible actions (as 3D touch has broader meaning). As mentioned by Buttfield-Addison, P., Manning, J., i wouldn't depend on this type of feedback. Since you have it in your app already and basing myself on the meaning of haptic (relating to the sense of touch, in particular relating to the perception and manipulation of objects using the senses of touch and proprioception), I reckon the long-press will remain as it's one of the possible touch interactions in the set of a normal / mainstream person's actions.
There's a good answer in apple.stackexchange I suggest you to read.