"If that was to happen the WTS will have to have a strong case, because a pure question of law or new issue will have to be presented by undisputed facts."
Well, that's true, but this is basically how all dismissal motions work, and appeals also. You basically have to say that even if we believe everything the other side says with respect to the facts, there is still no legal right to compensation, and therefore the case against you should be dismissed (or overturned on appeal).
My concern is that to my knowledge, a duty to protect ordinary members from one another on their own time has never been imposed on a religion before. Even if the California Supreme Court hasn't spoken on it either way, several other state supreme courts have said there is no such duty.
For example, from Maine:
"The creation of an amorphous common law duty on the part of a church or other voluntary organization requiring it to protect its members from each other would give rise to both unlimited liability and liability out of all proportion to culpability." Bryan R. v. Watchtower Bible & Tract Soc., 738 A.2d 839, 847 (Me. 1999).
Connecticut and New Hampshire have basically said the same thing, and likely other states as well. While the California Appeals courts are certainly not obligated to follow precedent from other states, I am concerned that they won't want to give their stamp of approval to a new duty that has been fairly widely rejected.