I like Touch ID...
...it's always been utterly reliable on my iPhone 6 Plus, so I'm watching the impact of Face ID with interest. The sort of interest that lets others spend their £1000 first. Given the need to hold the phone up to your face for Face ID, vs no such need for Touch ID, I can't see how Face ID could be better. But perhaps for those more intimately involved in their phone's front facing camera, it just means that unlocking your phone will be yet another selfie pose, so perhaps it'll work ok for them.
I've also reached 'peak phone' with my iPhone 6 Plus - it's thin enough, fast enough, has enough storage, a good enough camera, more than good enough screen - so I see no compelling reason to upgrade. I'm expecting to be in the minority here, though.