The idea that Aikido can be anything anyone wants it to be is a very generous idea. It is an extreme example of refusing to fight. I don't think that Gary, Katherine, or most Aikido artists would agree with that idea.
It doesn't matter whether I agree with it or not, as there's nothing I can do about it.
Certainly I can decide where and how I choose to train, and what I teach, but that's about the limit of my ability to influence things. Message board posts can encourage people to explore, but that's about it.
As for whether "aikido" -- for however you want to define it -- survives, that ultimately depends on whether aikido students are getting something they value out of their practice. If they are, it will. If not, it won't. If a particular approach appeals to more people, it will be more successful.
On the other hand, sheer number of students is not the only measure. Look at the koryu.