Why do you know that photos are not enough?
If you have good enough photos you can produce higher resolution 3D models than with a Kinect like depth sensor (which in the end is just a stereo "camera" anyway).
And since the Face ID probably does not work with any arbitrary 3D object but only with faces you just need to reconstruct the target face to a degree so that the Face ID system can detect the landmarks it is looking for.
My guess on how those attacks will develop in the future are:
1. Exploit occlusions.
As far as I know the FaceID System does work with occluded faces (glasses, maybe scarfs in the winter, ...). Once you know what the minimum required visible area is, you can focus on partial faces. If the algorithm has less features to identify, it probably makes more mistakes and is easier to fool.
2. Create a low-dimensional (in terms of parameters, not vertices) representation of a face that can be tuned to mimic a wide variety of target faces and still is correctly identified by Face ID. Once you have that you can take a few photos of your target person and tune the parameters in your generic model to fit the person in the photos, and probably be even able to reconstruct a mask from far away.
3. Try to create a real mask with a flexible surface that can be tuned to fit a wide range of faces. If at all possible try to span the same feature space as in 2.) as it would allow you to create a real face mask from only the few parameters that directly come from your fitting process.
If all of the above works an attacker can create an Iphone stealing pipeline:
Have several cameras set up in a crowded tourist spot. Match persons in different views and try to reconstruct their faces. Once the system has found a person that has been viewed from enough angles, "retrieve" his phone unlock it with the mask and reset it.
I know that does sound pessimistic, but your face is a "security token" but one which you can not realistically protect from theft. Unless you want it to have serious negative impact on your daily routine.
And if someone wants to hide his face while in public (i.e. with a surgical mask), he can no longer travel to certain countries. I live in Austria and there just recently came a law into effect that bars everyone from occluding their face while in public.