It seems to be coming out of the shadows on its own, since Ive moved to portland a year ago, almost everyone knows what the theremin is, has heard it, and Ive met several people who have made one or owned one, but most have just used it to make noise, or gave up because its too difficult to play. But still, I dont know if it is cause I live in portland now, and portland is a strange place, or if it is a function of time, but the number of "what is that?" have certainly gone down over time.
On another note, to me, the theremin has always been partially an idea, a instrument for the poletariat, a new instrument for a modern age. This idea failed, as the instrument is too hard to play, and the rca theremin was far too expensive, but, if you are looking for the heart or soul of a theremin, its more than a perfect sound, or vacuum tubes, part of it is the rejection of the aesthetic and social context of the violin or piano. While, little can be done to make it easier to play, but I think there is a danger of fetishizing the instrument itself. I always saw it as meant to be conceptually more of a folk instrument than a classical one. (Which I think is kept alive, in part, by its DIY nature, there are few classical instruments you can make a decent version of yourself, without significant skill and training)
And to call the etherwave and the b3 a toy, is a bit extreme. I understand your point on their limitations in tone, but they are practical, they can play a tune reliably, be thrown unceremoniously in the back of a van with a bunch of other gear, they could certainly sound better, but they are serviceable.