I don't think it's about whether or not the new iPhone will have Touch ID. Given its maturity and reliability, the question is more like: Where they are going to put Touch ID? Given heavy rumors on bezel-less design, it's only going to be either underneath the display or on the back of the device (maybe at the Apple logo directly?)
Even if they decide to ship iPhone 8 with Touch ID on the back, I still think it's going to be a huge upgrade since iPhone 6. OLED display will be very welcomed. 3D sensing will enable new functionalities. Wireless charging and fast charging will add more convenience. A large bezel-less design allowing big screen size in form factor that's easily held and used with one hand, while having significant extra batteries from stacked chips design, will be pleasant to have.
Really, if they manage to solve this production problem, this iPhone will probably be the most stunning and technologically attractive iPhone in its history. If not, it's still going to remain very attractive for prospective upgraders.