If the Voyage has actually sold 1/3 as much as the new Paperwhite then I don't think that's so bad since it's considerably more expensive with just about the same screen.
I read a few different forums and when readers mention their device the Voyage is mentioned quite a lot. It's not a rare thing at all.
I've been a Paperwhite reader since they first came out and I thought it was pretty much perfect till I got the Voyage. I don't use the extra features and I can't tell much difference in the screens while reading but I really like the flat surface and the smaller size and the lighter weight. While the Voyage might only weigh an ounce less than the Paperwhite, the Voyage and it's case, weighs less than half as much as the Paperwhite and it's case, even though the cases for both are pretty much the same. The extra size of the Paperwhite makes it's case a lot heavier. So it's a significant weight reduction.
I'm really not that sure how well the number of reviews correlates with the number of sales, either. It might be that we snobbish Voyage readers think of ourselves as above all that and don't bother writing reviews.
More realistically though, the Paperwhite is so good that a lot of people aren't motivated to get something else. I had decided not to get one and then one day I did on a whim. I felt kind of silly afterward, until it got here.
Barry