If the features in the new phone don't interest you, you're definitely not obligated to upgrade. In my case, I still use a 6S, so upgrading would actually mean losing features I still use, like 3D touch and a proper headphone jack. LIDAR sounds like it has great potential and I'd probably consider a new phone with it. But, like 3D touch, there's a risk that Apple will just drop the hardware if they don't think it gets used enough by app devs. So just consider what you prefer to have in a phone, and weigh it against what a new one gives and doesn't give you.